Hofmeister effect on the interfacial free energy of aliphatic and aromatic surfaces studied by chemical force microscopy.

PubMed

Patete, Jonathan; Petrofsky, John M; Stepan, Jeffery; Waheed, Abdul; Serafin, Joseph M

2009-01-15

This work describes chemical force microscopy (CFM) studies of specific-ion effects on the aqueous interfacial free energy of hydrophobic monolayers. CFM measurements allow for the characterization of interfacial properties on length scales below 100 nm. The ions chosen span the range of the Hofmeister series, from the kosmotropic Na(2)SO(4) to the chaotropic NaSCN. The salt concentrations used are typical of many laboratory processes such as protein crystallization, 2-3 M. Both aliphatic (terminal methyl) and aromatic (terminal phenyl) monolayers were examined, and rather pronounced differences were observed between the two cases. The specific-ion dependence of the aliphatic monolayer closely follows the Hofmeister series, namely the chaotropic ions lowered the interfacial free energy and the kosmotropic ions increased the interfacial free energy. However, the aromatic monolayer had significant deviations from the Hofmeister series. Possible origins for this difference are discussed.

Mixed ion/electron-conductive protective soft nanomatter-based conformal surface modification of lithium-ion battery cathode materials

NASA Astrophysics Data System (ADS)

Park, Jang-Hoon; Kim, Ju-Myung; Lee, Chang Kee; Lee, Sang-Young

2014-10-01

Understanding and control of interfacial phenomena between electrode material and liquid electrolytes are of major scientific importance for boosting development of high-performance lithium ion batteries with reliable electrochemical/safety attributes. Here, as an innovative surface engineering approach to address the interfacial issues, a new concept of mixed ion/electron-conductive soft nanomatter-based conformal surface modification of the cathode material is presented. The soft nanomatter is comprised of an electron conductive carbonaceous (C) substance embedded in an ion conductive polyimide (PI) nanothin compliant film. In addition to its structural uniqueness, the newly proposed surface modification benefits from a simple fabrication process. The PI/carbon soft nanomatter is directly synthesized on LiCoO2 surface via one-pot thermal treatment of polyamic acid (=PI precursor) and sucrose (=carbon source) mixture, where the LiCoO2 powders are chosen as a model system to explore the feasibility of this surface engineering strategy. The resulting PI/carbon coating layer facilitates electronic conduction and also suppresses unwanted side reactions arising from the cathode material-liquid electrolyte interface. These synergistic coating effects of the multifunctional PI/carbon soft nanomatter significantly improve high-voltage cell performance and also mitigate interfacial exothermic reaction between cathode material and liquid electrolyte.

Thermal annealing and transient electronic excitations induced interfacial and magnetic effects on Pt/Co/Pt trilayer

NASA Astrophysics Data System (ADS)

Sehdev, Neeru; Medwal, Rohit; Malik, Rakesh; Kandasami, Asokan; Kanjilal, Dinakar; Annapoorni, S.

2018-04-01

Present study investigates the importance of thermal annealing and transient electronic excitations (using 100 MeV oxygen ions) in assisting the interfacial atomic diffusion, alloy composition, and magnetic switching field distributions in Pt/Co/Pt stacked trilayer. X-ray diffraction analysis reveals that thermal annealing results in the formation of the face centered tetragonal L1°CoPt phase. The Rutherford back scattering spectra shows a trilayer structure for as-deposited and as-irradiated films. Interlayer mixing on the thermally annealed films further improves by electronic excitations produced by high energy ion irradiation. Magnetically hard face centered tetragonal CoPt alloy retains its hard phase after ion irradiation and reveals an enhancement in the structural ordering and magnetic stability. Enhancement in the homogeneity of alloy composition and its correlation with the magnetic switching field is evident from this study. A detailed investigation of the contributing parameters shows that the magnetic switching behaviour varies with the type of thermal annealing, transient electronic excitations of ion beams and combination of these processes.

Oxygen deficiency induced deterioration in microstructure and magnetic properties at Y{sub 3}Fe{sub 5}O{sub 12}/Pt interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Dongsheng; Zhu, Jing, E-mail: jzhu@mail.tsinghua.edu.cn; Ma, Li

2015-07-27

Transport efficiency of pure spin current across the ferromagnetic films adjacent with a nonmagnetic metal is strongly dependent on the spin mixing conductance, which is very sensitive to atomic-level interface conditions. Here, by the means of advanced electron microscopy techniques, atomic structure, electronic structure, and magnetic properties at Y{sub 3}Fe{sub 5}O{sub 12} (YIG)/Pt interface are detailed characterized to correlate the microstructure and magnetic properties with interfacial transport properties. It is found that the order-disorder structure transformation at the interface is accompanied with oxygen deficiency, thus the reduced iron valence and the break of magnetic atom-O-magnetic atom bridges, which is responsiblemore » for superexchange interaction and magnetic order. It is also found that the magnetic moment of interfacial iron ions is decreased. The disorder interfacial layer with suppressed magnetism finally contributes to the declined spin transport efficiency. Our results provide the knowledge to control and manipulate the interfacial structure and properties in order to obtain higher spin transport efficiency.« less

Interface Engineering of Garnet Solid Electrolytes

NASA Astrophysics Data System (ADS)

Cheng, Lei

Solid lithium ion conductors represent a promising class of materials for next generation high energy density batteries, with the potential for enabling use of high capacity Li metal anodes and providing opportunities for novel lithium-free cathode materials. However, highly resistive interfaces stymie their practical use. This urgent scientific challenge requires mechanistic understanding of ion transport at interfaces, as well as development of novel processes to achieve low interfacial resistances. The goal of this PhD dissertation was to generate fundamental understandings of garnet-structured Al substituted Li7La3Zr2O 12 (LLZO) electrolyte surfaces and interfaces with lithium metal electrodes. Specifically in this research, the topmost surface microstructure, local chemical environment, and surface chemistry were carefully studied. The ceramic processing of garnet is discussed and ways to control the sintering behavior and microstructures were explored and successfully demonstrated. Factors contributing to high interfacial resistance were systematically studied. The source of the high interfacial impedance has been traced to the presence of Li2CO 3 on pellet surfaces resulting from air exposure after processing. In addition, it was discovered that surface grain boundaries are surprisingly fast ion transport pathways and surface microstructure is critically important to lithium ion transport at interfaces. Complex homo- and heterostructured LLZO solid electrolytes with controllable surface and bulk microstructures were successfully fabricated, which allowed the comparison and separation of the contribution from the surface and the bulk. Engineered pellet surfaces allowed us to achieve the lowest interfacial resistance ever reported for this composition, resulting in significantly improved cycling behavior. Lastly, it was found that LLZO surfaces can be effectively stabilized under air exposure conditions, preventing Li2CO3 formation and maintaining low interfacial resistances. This opens new opportunities for garnet solid electrolyte in practical applications.

Ion dynamics in a new class of materials: nanoglassy lithium alumosilicates

NASA Astrophysics Data System (ADS)

Stanje, B.; Bottke, P.; Breuer, S.; Hanzu, I.; Heitjans, P.; Wilkening, M.

2018-03-01

In many cases nanocrystalline materials, prepared through high-energy ball milling, reveal enhanced ion dynamics when compared to the situation in the coarse-grained analogues. This effect, which has particularly been seen for lithium alumosilicates, has been ascribed to structural disorder, i.e., the introduction of defect sites during mechanical treatment. Much less is, however, known about ion transport in nanostructured amorphous materials, e.g., nanoglassy compounds, which are regarded as a new class of functional materials. Following earlier studies on nanoglassy lithium alumosilicates and borates, here we studied ion dynamics in nanoglassy petalite LiAlSi4O10. While conductivity spectroscopy unequivocally reveals that long-range ion dynamics in nanoglassy LiAlSi4O10 decreases upon milling, local dynamics, sensed by 7Li nuclear magnetic resonance (NMR) spin-lattice relaxation, points to enhanced Li ion mobility compared to the non-treated glass. Most likely, as for nanocrystalline ceramics also for nanoglassy samples a heterogeneous structure, consisting of bulk and interfacial regions, is formed. For LiAlSi4O10 these interfacial regions, characterized by a higher degree of free volume, might act as hosts for spins experiencing fast longitudinal NMR relaxation. Obviously, these regions do not form a through-going network, which would allow the ions to move over long distances as quickly as in the unmilled glass.

Compositional and structural analysis of nitrogen incorporated and ion implanted diamond thin films

NASA Astrophysics Data System (ADS)

Garratt, Elias James

Significant progress in area of nano-structured thin film systems has taken place in recent decades. In particular, diamond thin film systems are being widely studied for their wear resistant, optical and electronic properties. Of the various methods researchers use to modify the structure of such films, three techniques in particular are of interest due to their versatility: modification of the growth atmosphere, growth on metalized substrates, providing an interfacial layer, and modification through post-growth ion implantation. The aim of this study is to investigate the effects each has to the structure and composition of elements. Different techniques are applied in each section; nitrogen gas dilution in a microwave plasma CVD system, diamond deposition on a metal interfacial layer and ion implantation in thin nanocrystalline diamond film. The forms of nanocrystalline diamond film resulting from such modifications are investigated using advanced spectroscopic and spectrometric techniques, as well as mechanical testing and surface mapping. The impact of these characterizations will provide valuable perspective to researchers in materials science. Understanding the changes to the structure and properties of this class of thin films, which can be induced through various mechanisms, will allow future researchers to refine these films towards technological applications in areas of hard coatings, electronics and photonics.

A Synopsis of Interfacial Phenomena in Lithium-Based Polymer Electrolyte Electrochemical Cells

NASA Technical Reports Server (NTRS)

Baldwin, Richard S.; Bennett, William R.

2007-01-01

The interfacial regions between electrode materials, electrolytes and other cell components play key roles in the overall performance of lithium-based batteries. For cell chemistries employing lithium metal, lithium alloy or carbonaceous materials (i.e., lithium-ion cells) as anode materials, a "solid electrolyte interphase" (SEI) layer forms at the anode/electrolyte interface, and the properties of this "passivating" layer significantly affect the practical cell/battery quality and performance. A thin, ionically-conducting SEI on the electrode surface can beneficially reduce or eliminate undesirable side reactions between the electrode and the electrolyte, which can result in a degradation in cell performance. The properties and phenomena attributable to the interfacial regions existing at both anode and cathode surfaces can be characterized to a large extent by electrochemical impedance spectroscopy (EIS) and related techniques. The intention of the review herewith is to support the future development of lithium-based polymer electrolytes by providing a synopsis of interfacial phenomena that is associated with cell chemistries employing either lithium metal or carbonaceous "composite" electrode structures which are interfaced with polymer electrolytes (i.e., "solvent-free" as well as "plasticized" polymer-binary salt complexes and single ion-conducting polyelectrolytes). Potential approaches to overcoming poor cell performance attributable to interfacial effects are discussed.

Stern Layer Structure and Energetics at Mica-Water Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourg, Ian C.; Lee, Sang Soo; Fenter, Paul

2017-04-11

The screening of surface charge by dissolved ions at solid liquid interfaces in the region of interfacial fluid known as the electrical double layer (EDL)-plays a recurrent role in surface science, from ion adsorption to colloidal mechanics to the transport properties of nanoporous media. A persistent unknown in theories of EDL-related phenomena is the structure of the Stern layer, the near-surface portion of the EDL where water molecules and adsorbed ions form specific short-range interactions with surface atoms. Here, we describe a set of synchrotron X-ray reflectivity (XRR) experiments and molecular dynamics (MD) simulations carried out under identical conditions formore » a range of 0.1 M alkali chloride (Li-, Na-, K-, Rb-, or CsCl) solutions on the basal surface of muscovite mica, a mineral isostructural to phyllosilicate clay minerals and one of the most widely studied reference surfaces in interfacial science. Our XRR and MD simulation results provide a remarkably consistent view of the structure and energetics of the Stern layer, with some discrepancy on the fraction of the minor outer-sphere component of Rb and on the adsorption energetics of Li. The results of both techniques, along with surface complexation model calculations, provide insight into the sensitivity of water structure and ion adsorption to surface topography and the type of adsorbed counterion.« less

Ion adsorption at the rutile-water interface: linking molecular and macroscopic properties.

PubMed

Zhang, Z; Fenter, P; Cheng, L; Sturchio, N C; Bedzyk, M J; Predota, M; Bandura, A; Kubicki, J D; Lvov, S N; Cummings, P T; Chialvo, A A; Ridley, M K; Bénézeth, P; Anovitz, L; Palmer, D A; Machesky, M L; Wesolowski, D J

2004-06-08

A comprehensive picture of the interface between aqueous solutions and the (110) surface of rutile (alpha-TiO2) is being developed by combining molecular-scale and macroscopic approaches, including experimental measurements, quantum calculations, molecular simulations, and Gouy-Chapman-Stern models. In situ X-ray reflectivity and X-ray standing-wave measurements are used to define the atomic arrangement of adsorbed ions, the coordination of interfacial water molecules, and substrate surface termination and structure. Ab initio calculations and molecular dynamics simulations, validated through direct comparison with the X-ray results, are used to predict ion distributions not measured experimentally. Potentiometric titration and ion adsorption results for rutile powders having predominant (110) surface expression provide macroscopic constraints of electrical double layer (EDL) properties (e.g., proton release) which are evaluated by comparison with a three-layer EDL model including surface oxygen proton affinities calculated using ab initio bond lengths and partial charges. These results allow a direct correlation of the three-dimensional, crystallographically controlled arrangements of various species (H2O, Na+, Rb+, Ca2+, Sr2+, Zn2+, Y3+, Nd3+) with macroscopic observables (H+ release, metal uptake, zeta potential) and thermodynamic/electrostatic constraints. All cations are found to be adsorbed as "inner sphere" species bonded directly to surface oxygen atoms, while the specific binding geometries and reaction stoichiometries are dependent on ionic radius. Ternary surface complexes of sorbed cations with electrolyte anions are not observed. Finally, surface oxygen proton affinities computed using the MUSIC model are improved by incorporation of ab initio bond lengths and hydrogen bonding information derived from MD simulations. This multitechnique and multiscale approach demonstrates the compatibility of bond-valence models of surface oxygen proton affinities and Stern-based models of the EDL structure, with the actual molecular interfacial distributions observed experimentally, revealing new insight into EDL properties including specific binding sites and hydration states of sorbed ions, interfacial solvent properties (structure, diffusivity, dielectric constant), surface protonation and hydrolysis, and the effect of solution ionic strength.

Dopant-Modulating Mechanism of Lithium Adsorption and Diffusion at the Graphene /Li2S Interface

NASA Astrophysics Data System (ADS)

Guo, Lichao; Li, Jiajun; Wang, Huayu; Zhao, Naiqin; Shi, Chunsheng; Ma, Liying; He, Chunnian; He, Fang; Liu, Enzuo

2018-02-01

Graphene modification is one of the most effective routes to enhance the electrochemical properties of the transition-metal sulfide anode for Li-ion batteries and the Li2S cathode for Li-S batteries. Boron, nitrogen, oxygen, phosphorus, and sulfur doping greatly affect the electrochemical properties of Li2S /graphene . Here, we investigate the interfacial binding energy, lithium adsorption energy, interface diffusion barrier, and electronic structure by first-principles calculations to unveil the diverse effects of different dopants during interfacial lithiation reactions. The interfacial lithium storage follows the pseudocapacitylike mechanism with intercalation character. Two different mechanisms are revealed to enhance the interfacial lithium adsorption and diffusion, which are the electron-deficiency host doping and the vacancylike structure evolutions with bond breaking. The synergistic effect between different dopants with diverse doping effects is also proposed. The results give a theoretical basis for the materials design with doped graphene as advanced materials modification for energy storage.

Membrane formation in liquids by adding an antagonistic salt

NASA Astrophysics Data System (ADS)

Sadakane, Koichiro; Seto, Hideki

2018-03-01

Antagonistic salts are composed of hydrophilic and hydrophobic ions. In a binary mixture, such as water and organic solvent, these ion pairs preferentially dissolve to those phases, respectively, and there is a coupling between the charge density and the composition. The heterogeneous distribution of ions forms a large electric double layer at the interface between these solvents. This reduces the interfacial tension between water and organic solvent, and stabilizes an ordered structure, such as a membrane. These phenomena have been extensively studied from both theoretical and experimental point of view. In addition, the numerical simulations can reproduce such ordered structures.

Insights into the structural effects of layered cathode materials for high voltage sodium-ion batteries

DOE PAGES

Xu, Gui -Liang; Amine, Rachid; Xu, Yue -Feng; ...

2017-06-08

Cathode materials are critical to the energy density, power density and safety of sodium-ion batteries (SIBs). Herein, we performed a comprehensive study to elucidate and exemplify the interplay mechanism between phase structures, interfacial microstrain and electrochemical properties of layered-structured Na xNi 1/3Co 1/3Mn 1/3O 2 cathode materials for high voltage SIBs. The electrochemical test results showed that Na xNi 1/3Co 1/3Mn 1/3O 2 with an intergrowth P2/O3/O1 structure demonstrates better electrochemical performance and better thermal stability than Na xNi 1/3Co 1/3Mn 1/3O 2 with P2/O3 binary-phase integration and Na xNi 1/3Co 1/3Mn 1/3O 2 where only the P phase ismore » dominant. This result is caused by the distinct interfacial microstrain development during the synthesis and cycling of the P2/O3/O1 phase. In operando high energy X-ray diffraction further revealed that the intergrowth P2/O1/O3 cathode can inhibit the irreversible P2–O2 phase transformation and simultaneously improve the structure stability of the O3 and O1 phases during cycling. Here, we believe that interfacial microstrain can serve as an indispensable bridge to guide future design and synthesis of high performance SIB cathode materials and other high energy battery materials.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donald, Scott B.; Siekhaus, Wigbert J.; Nelson, Art J.

X-ray photoelectron spectroscopy in combination with secondary ion mass spectrometry depth profiling were used to investigate the surface and interfacial chemistry of C + ion implanted polycrystalline uranium subsequently oxidized in air for over 10 years at ambient temperature. The original implantation of 33 keV C + ions into U 238 with a dose of 4.3 × 10 17 cm –3 produced a physically and chemically modified surface layer that was characterized and shown to initially prevent air oxidation and corrosion of the uranium after 1 year in air at ambient temperature. The aging of the surface and interfacial layersmore » were examined by using the chemical shift of the U 4f, C 1s, and O 1s photoelectron lines. In addition, valence band spectra were used to explore the electronic structure of the aged carbide surface and interface layer. Moreover, the time-of-flight secondary ion mass spectrometry depth profiling results for the aged sample confirmed an oxidized uranium carbide layer over the carbide layer/U metal interface.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Jacob W.; Lam, Royce K.; Saykally, Richard J., E-mail: saykally@berkeley.edu

Nitrate and nitrite ions are of considerable interest, both for their widespread use in commercial and research contexts and because of their central role in the global nitrogen cycle. The chemistry of atmospheric aerosols, wherein nitrate is abundant, has been found to depend on the interfacial behavior of ionic species. The interfacial behavior of ions is determined largely by their hydration properties; consequently, the study of the hydration and interfacial behavior of nitrate and nitrite comprises a significant field of study. In this work, we describe the study of aqueous solutions of sodium nitrate and nitrite via X-ray absorption spectroscopymore » (XAS), interpreted in light of first-principles density functional theory electronic structure calculations. Experimental and calculated spectra of the nitrogen K-edge XA spectra of bulk solutions exhibit a large 3.7 eV shift between the XA spectra of nitrate and nitrite resulting from greater stabilization of the nitrogen 1s energy level in nitrate. A similar shift is not observed in the oxygen K-edge XA spectra of NO{sub 3}{sup −} and NO{sub 2}{sup −}. The hydration properties of nitrate and nitrite are found to be similar, with both anions exhibiting a similar propensity towards ion pairing.« less

In Situ STEM-EELS observation of nanoscale interfacial phenomena in all-solid-state batteries

DOE PAGES

Wang, Ziying; Santhanagopalan, Dhamodaran; Zhang, Wei; ...

2016-05-03

Behaviors of functional interfaces are crucial factors in the performance and safety of energy storage and conversion devices. Indeed, solid electrode–solid electrolyte interfacial impedance is now considered the main limiting factor in all-solid-state batteries rather than low ionic conductivity of the solid electrolyte. In this paper, we present a new approach to conducting in situ scanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS) in order to uncover the unique interfacial phenomena related to lithium ion transport and its corresponding charge transfer. Our approach allowed quantitative spectroscopic characterization of a galvanostatically biased electrochemical system under in situmore » conditions. Using a LiCoO 2/LiPON/Si thin film battery, an unexpected structurally disordered interfacial layer between LiCoO 2 cathode and LiPON electrolyte was discovered to be inherent to this interface without cycling. During in situ charging, spectroscopic characterization revealed that this interfacial layer evolved to form highly oxidized Co ions species along with lithium oxide and lithium peroxide species. These findings suggest that the mechanism of interfacial impedance at the LiCoO 2/LiPON interface is caused by chemical changes rather than space charge effects. Finally, insights gained from this technique will shed light on important challenges of interfaces in all-solid-state energy storage and conversion systems and facilitate improved engineering of devices operated far from equilibrium.« less

Combination of first-principles molecular dynamics and XANES simulations for LiCoO2-electrolyte interfacial reactions in a lithium-ion battery

NASA Astrophysics Data System (ADS)

Tamura, Tomoyuki; Kohyama, Masanori; Ogata, Shuji

2017-07-01

We performed a first-principles molecular dynamics (FPMD) simulation of the interfacial reactions between a LiCoO2 electrode and a liquid ethylene carbonate (EC) electrolyte. For configurations during the FPMD simulation, we also performed first-principles Co K-edge x-ray absorption near-edge structure (XANES) simulations, which can properly reproduce the bulk and surface spectra of LiCoO2. We observed strong absorption of an EC molecule on the LiCoO2 {110} surface, involving ring opening of the molecule, bond formation between oxygen atoms in the molecule and surface Co ions, and emission of one surface Li ion, while all the surface Co ions remain Co3 +. The surface Co ions having the bond with an oxygen atom in the molecule showed remarkable changes in simulated K-edge spectra which are similar to those of the in situ observation under electrolyte soaking [D. Takamatsu et al., Angew. Chem., Int. Ed. 51, 11597 (2012), 10.1002/anie.201203910]. Thus, the local environmental changes of surface Co ions due to the reactions with an EC molecule can explain the experimental spectrum changes.

Electrostatic Properties of Aqueous Salt Solution Interfaces: A Comparison of Polarizable and Non-Polarizable Ion Models

PubMed Central

Warren, G. Lee; Patel, Sandeep

2014-01-01

The effects of ion force field polarizability on the interfacial electrostatic properties of ~1 M aqueous solutions of NaCl, CsCl and NaI are investigated using molecular dynamics simulations employing both non-polarizable and Drude-polarizable ion sets. Differences in computed depth-dependent orientational distributions, “permanent” and induced dipole and quadrupole moment profiles, and interfacial potentials are obtained for both ion sets to further elucidate how ion polarizability affects interfacial electrostatic properties among the various salts relative to pure water. We observe that the orientations and induced dipoles of water molecules are more strongly perturbed in the presence of polarizable ions via a stronger ionic double layer effect arising from greater charge separation. Both anions and cations exhibit enhanced induced dipole moments and strong z alignment in the vicinity of the Gibbs dividing surface (GDS) with the magnitude of the anion induced dipoles being nearly an order of magnitude larger than those of the cations and directed into the vapor phase. Depth-dependent profiles for the trace and zz components of the water molecular quadrupole moment tensors reveal 40% larger quadrupole moments in the bulk phase relative to the vapor mimicking a similar observed 40% increase in the average water dipole moment. Across the GDS, the water molecular quadrupole moments increase non-monotonically (in contrast to the water dipoles) and exhibit a locally reduced contribution just below the surface due to both orientational and polarization effects. Computed interfacial potentials for the non-polarizable salts yield values 20 to 60 mV more positive than pure water and increase by an additional 30 to 100 mV when ion polarizability is included. A rigorous decomposition of the total interfacial potential into ion monopole, water and ion dipole, and water quadrupole components reveals that a very strong, positive ion monopole contribution is offset by negative contributions from all other potential sources. Water quadrupole components modulated by the water density contribute significantly to the observed interfacial potential increments and almost entirely explain observed differences in the interfacial potentials for the two chloride salts. By lumping all remaining non-quadrupole interfacial potential contributions into a single “effective” dipole potential, we observe that the ratio of quadrupole to “effective” dipole contributions range from 2:1 in CsCl to 1:1.5 in NaI suggesting that both contributions are comparably important in determining the interfacial potential increments. We also find that oscillations in the quadrupole potential in the double layer region are opposite in sign and partially cancel those of the “effective” dipole potential. PMID:18712908

Coupling of semiconductor nanowires with neurons and their interfacial structure.

PubMed

Lee, Ki-Young; Shim, Sojung; Kim, Il-Soo; Oh, Hwangyou; Kim, Sunoh; Ahn, Jae-Pyeong; Park, Seung-Han; Rhim, Hyewhon; Choi, Heon-Jin

2009-12-04

We report on the compatibility of various nanowires with hippocampal neurons and the structural study of the neuron-nanowire interface. Si, Ge, SiGe, and GaN nanowires are compatible with hippocampal neurons due to their native oxide, but ZnO nanowires are toxic to neuron due to a release of Zn ion. The interfaces of fixed Si nanowire and hippocampal neuron, cross-sectional samples, were prepared by focused ion beam and observed by transmission electron microscopy. The results showed that the processes of neuron were adhered well on the nanowire without cleft.

Geometric and energetic considerations of surface fluctuations during ion transfer across the water-immiscible organic liquid interface

NASA Astrophysics Data System (ADS)

Karnes, John J.; Benjamin, Ilan

2016-07-01

Molecular dynamics simulations and umbrella sampling free energy calculations are used to examine the thermodynamics, energetics, and structural fluctuations that accompany the transfer of a small hydrophilic ion (Cl-) across the water/nitrobenzene interface. By examining several constrained interface structures, we isolate the energetic costs of interfacial deformation and co-transfer of hydration waters during the ion transfer. The process is monitored using both energy-based solvation coordinates and a geometric coordinate recently introduced by Morita and co-workers to describe surface fluctuations. Our simulations show that these coordinates provide a complimentary description of the water surface fluctuations during the transfer and are necessary for elucidating the mechanism of the ion transfer.

Molecular dynamics investigation on adsorption layer of alcohols at the air/brine interface.

PubMed

Nguyen, Cuong V; Phan, Chi M; Ang, Ha M; Nakahara, Hiromichi; Shibata, Osamu; Moroi, Yoshikiyo

2015-01-01

Alcohols are a significant group of surfactants which have been employed extensively in industry to improve the interfacial effects. Recently, the change in surface potential (ΔV) of two isomeric hexanols, methyl isobutyl carbinol (MIBC) and 1-hexanol, was investigated by using an ionizing (241)Am electrode. It clearly showed the opposite effects between MIBC and 1-hexanol in the interfacial zone: one enhanced the presence of cations, whereas the other enhanced the presence of anions. This study employs molecular dynamics simulation to provide new insights into the interactions between alcohol molecules and ions as well as water at the molecular level. The results qualitatively agreed with the experimental data and verified the significance of MIBC branching structure on the molecular arrangement within the interfacial zone. The results also highlighted the role of the second water layer on the interfacial properties.

Magneto-ionic control of interfacial magnetism

NASA Astrophysics Data System (ADS)

Bauer, Uwe; Yao, Lide; Tan, Aik Jun; Agrawal, Parnika; Emori, Satoru; Tuller, Harry L.; van Dijken, Sebastiaan; Beach, Geoffrey S. D.

2015-02-01

In metal/oxide heterostructures, rich chemical, electronic, magnetic and mechanical properties can emerge from interfacial chemistry and structure. The possibility to dynamically control interface characteristics with an electric field paves the way towards voltage control of these properties in solid-state devices. Here, we show that electrical switching of the interfacial oxidation state allows for voltage control of magnetic properties to an extent never before achieved through conventional magneto-electric coupling mechanisms. We directly observe in situ voltage-driven O2- migration in a Co/metal-oxide bilayer, which we use to toggle the interfacial magnetic anisotropy energy by >0.75 erg cm-2 at just 2 V. We exploit the thermally activated nature of ion migration to markedly increase the switching efficiency and to demonstrate reversible patterning of magnetic properties through local activation of ionic migration. These results suggest a path towards voltage-programmable materials based on solid-state switching of interface oxygen chemistry.

What Can We Learn from Solid State NMR on the Electrode-Electrolyte Interface?

PubMed

Haber, Shira; Leskes, Michal

2018-06-11

Rechargeable battery cells are composed of two electrodes separated by an ion-conducting electrolyte. While the energy density of the cell is mostly determined by the redox potential of the electrodes and amount of charge they can store, the processes at the electrode-electrolyte interface govern the battery's lifetime and performance. Viable battery cells rely on unimpeded ion transport across this interface, which depends on its composition and structure. These properties are challenging to determine as interfacial phases are thin, disordered, heterogeneous, and can be very reactive. The recent developments and applications of solid state NMR spectroscopy in the study of interfacial phenomena in rechargeable batteries based on lithium and sodium chemistries are reviewed. The different NMR interactions are surveyed and how these are used to shed light on the chemical composition and architecture of interfacial phases as well as directly probe ion transport across them is described. By combining new methods in solid state NMR spectroscopy with other analytical tools, a holistic description of the electrode-electrolyte interface can be obtained. This will enable the design of improved interfaces for developing battery cells with high energy, high power, and longer lifetime. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Understanding the role of ion interactions in soluble salt flotation with alkylammonium and alkylsulfate collectors.

PubMed

Ozdemir, Orhan; Du, Hao; Karakashev, Stoyan I; Nguyen, Anh V; Celik, M S; Miller, Jan D

2011-03-15

There is anecdotal evidence for the significant effects of salt ions on the flotation separation of minerals using process water of high salt content. Examples include flotation of soluble salt minerals such as potash, trona and borax in brine solutions using alkylammonium and alkylsulfate collectors such as dodecylamine hydrochloride and sodium dodecylsulfate. Although some of the effects are expected, some do not seem to be encompassed by classical theories of colloid science. Several experimental and modeling techniques for determining solution viscosity, surface tension, bubble-particle attachment time, contact angle, and molecular dynamics simulation have been used to provide further information on air-solution and solid-solution interfacial phenomena, especially with respect to the interfacial water structure due to the presence of dissolved ions. In addition atomic force microscopy, and sum frequency generation vibrational spectroscopy have been used to provide further information on surface states. These studies indicate that the ion specificity effect is the most significant factor influencing flotation in brine solutions. Copyright © 2011 Elsevier B.V. All rights reserved.

XPS and SIMS study of the surface and interface of aged C + implanted uranium

DOE PAGES

Donald, Scott B.; Siekhaus, Wigbert J.; Nelson, Art J.

2016-09-08

X-ray photoelectron spectroscopy in combination with secondary ion mass spectrometry depth profiling were used to investigate the surface and interfacial chemistry of C + ion implanted polycrystalline uranium subsequently oxidized in air for over 10 years at ambient temperature. The original implantation of 33 keV C + ions into U 238 with a dose of 4.3 × 10 17 cm –3 produced a physically and chemically modified surface layer that was characterized and shown to initially prevent air oxidation and corrosion of the uranium after 1 year in air at ambient temperature. The aging of the surface and interfacial layersmore » were examined by using the chemical shift of the U 4f, C 1s, and O 1s photoelectron lines. In addition, valence band spectra were used to explore the electronic structure of the aged carbide surface and interface layer. Moreover, the time-of-flight secondary ion mass spectrometry depth profiling results for the aged sample confirmed an oxidized uranium carbide layer over the carbide layer/U metal interface.« less

The Significance of Interfacial Water Structure in Soluble Salt Flotation Systems.

PubMed

Hancer, M.; Celik, M. S.; Miller, J. D.

2001-03-01

Flotation of soluble salts with dodecyl amine hydrochloride (DAH) and sodium dodecyl sulfate (SDS) collectors has demonstrated that the interfacial water structure and hydration states of soluble salt surfaces together with the precipitation tendency of the corresponding collector salts are of considerable importance in explaining their flotation behavior. In particular, the high concentration of ions in these soluble salt brines and their hydration appear to modify the bulk and interfacial structure of water as revealed by contact angle measurements and this effect is shown to be an important feature in the flotation chemistry of soluble salt minerals including alkali halide and alkali oxyanion salts. Depending on characteristic chemical features (salt type), the salt can serve either as a structure maker, in which intermolecular hydrogen bonding between water molecules is facilitated, or as a structure breaker, in which intermolecular hydrogen bonding between water molecules is disrupted. For structure making salts the brine completely wets the salt surface and no contact angle can be measured. For structure breaking salts the brine does not completely wet the salt surface and a finite contact angle is measured. In this regard it has been found that soluble salt flotation either with the cationic DAH or anionic SDS collector is possible only if the salt is a structure breaker. Copyright 2001 Academic Press.

Accessing the bottleneck in all-solid state batteries, lithium-ion transport over the solid-electrolyte-electrode interface.

PubMed

Yu, Chuang; Ganapathy, Swapna; Eck, Ernst R H van; Wang, Heng; Basak, Shibabrata; Li, Zhaolong; Wagemaker, Marnix

2017-10-20

Solid-state batteries potentially offer increased lithium-ion battery energy density and safety as required for large-scale production of electrical vehicles. One of the key challenges toward high-performance solid-state batteries is the large impedance posed by the electrode-electrolyte interface. However, direct assessment of the lithium-ion transport across realistic electrode-electrolyte interfaces is tedious. Here we report two-dimensional lithium-ion exchange NMR accessing the spontaneous lithium-ion transport, providing insight on the influence of electrode preparation and battery cycling on the lithium-ion transport over the interface between an argyrodite solid-electrolyte and a sulfide electrode. Interfacial conductivity is shown to depend strongly on the preparation method and demonstrated to drop dramatically after a few electrochemical (dis)charge cycles due to both losses in interfacial contact and increased diffusional barriers. The reported exchange NMR facilitates non-invasive and selective measurement of lithium-ion interfacial transport, providing insight that can guide the electrolyte-electrode interface design for future all-solid-state batteries.

Graphene Visualizes the Ion Distribution on Air-Cleaved Mica.

PubMed

Bampoulis, Pantelis; Sotthewes, Kai; Siekman, Martin H; Zandvliet, Harold J W; Poelsema, Bene

2017-03-06

The distribution of potassium (K + ) ions on air-cleaved mica is important in many interfacial phenomena such as crystal growth, self-assembly and charge transfer on mica. However, due to experimental limitations to nondestructively probe single ions and ionic domains, their exact lateral organization is yet unknown. We show, by the use of graphene as an ultra-thin protective coating and scanning probe microscopies, that single potassium ions form ordered structures that are covered by an ice layer. The K + ions prefer to minimize the number of nearest neighbour K + ions by forming row-like structures as well as small domains. This trend is a result of repulsive ionic forces between adjacent ions, weakened due to screening by the surrounding water molecules. Using high resolution conductive atomic force microscopy maps, the local conductance of the graphene is measured, revealing a direct correlation between the K + distribution and the structure of the ice layer. Our results shed light on the local distribution of ions on the air-cleaved mica, solving a long-standing enigma. They also provide a detailed understanding of charge transfer from the ionic domains towards graphene.

An insight into intrinsic interfacial properties between Li metals and Li10GeP2S12 solid electrolytes.

PubMed

Chen, Bingbing; Ju, Jiangwei; Ma, Jun; Zhang, Jianjun; Xiao, Ruijuan; Cui, Guanglei; Chen, Liquan

2017-11-29

Density functional theory simulations and experimental studies were performed to investigate the interfacial properties, including lithium ion migration kinetics, between lithium metal anode and solid electrolyte Li 10 GeP 2 S 12 (LGPS). The LGPS[001] plane was chosen as the studied surface because the easiest Li + migration pathway is along this direction. The electronic structure of the surface states indicated that the electrochemical stability was reduced at both the PS 4 - and GeS 4 -teminated surfaces. For the interface cases, the equilibrium interfacial structures of lithium metal against the PS 4 -terminated LGPS[001] surface (Li/PS 4 -LGPS) and the GeS 4 -terminated LGPS[001] surface (Li/GeS 4 -LGPS) were revealed based on the structural relaxation and adhesion energy analysis. Solid electrolyte interphases were expected to be formed at both Li/PS 4 -LGPS and Li/GeS 4 -LGPS interfaces, resulting in an unstable state of interface and large interfacial resistance, which was verified by the EIS results of the Li/LGPS/Li cell. In addition, the simulations of the migration kinetics show that the energy barriers for Li + crossing the Li/GeS 4 -LGPS interface were relatively low compared with the Li/PS 4 -LGPS interface. This may contribute to the formation of Ge-rich phases at the Li/LGPS interface, which can tune the interfacial structures to improve the ionic conductivity for future all-solid-state batteries. This work will offer a thorough understanding of the Li/LGPS interface, including local structures, electronic states and Li + diffusion behaviors in all-solid-state batteries.

Reaction Dynamics at Liquid Interfaces

NASA Astrophysics Data System (ADS)

Benjamin, Ilan

2015-04-01

The liquid interface is a narrow, highly anisotropic region, characterized by rapidly varying density, polarity, and molecular structure. I review several aspects of interfacial solvation and show how these affect reactivity at liquid/liquid interfaces. I specifically consider ion transfer, electron transfer, and SN2 reactions, showing that solvent effects on these reactions can be understood by examining the unique structure and dynamics of the liquid interface region.

Development of FRP composite structural biomaterials: ultimate strength of the fiber/matrix interfacial bond in in vivo simulated environments.

PubMed

Latour, R A; Black, J

1992-05-01

Fiber reinforced polymer (FRP) composites are being developed as alternatives to metals for structural orthopedic implant applications. FRP composite fracture behavior and environmental interactions are distinctly different from those which occur in metals. These differences must be accounted for in the design and evaluation of implant performance. Fiber/matrix interfacial bond strength in a FRP composite is known to strongly influence fracture behavior. The interfacial bond strength of four candidate fiber/matrix combinations (carbon fiber/polycarbonate, carbon fiber/polysulfone, polyaramid fiber/polycarbonate, polyaramid fiber/polysulfone) were investigated at 37 degrees C in dry and in vivo simulated (saline, exudate) environments. Ultimate bond strength was measured by a single fiber-microdroplet pull-out test. Dry bond strengths were significantly decreased following exposure to either saline or exudate with bond strength loss being approximately equal in both the saline and exudate. Bond strength loss is attributed to the diffusion of water and/or salt ions into the sample and their interaction with interfacial bonding. Because bond degradation is dependent upon diffusion, diffusional equilibrium must be obtained in composite test samples before the full effect of the test environment upon composite mechanical behavior can be determined.

Operando X-ray Investigation of Electrode/Electrolyte Interfaces in Model Solid Oxide Fuel Cells

PubMed Central

2016-01-01

We employed operando anomalous surface X-ray diffraction to investigate the buried interface between the cathode and the electrolyte of a model solid oxide fuel cell with atomic resolution. The cell was studied under different oxygen pressures at elevated temperatures and polarizations by external potential control. Making use of anomalous X-ray diffraction effects at the Y and Zr K-edges allowed us to resolve the interfacial structure and chemical composition of a (100)-oriented, 9.5 mol % yttria-stabilized zirconia (YSZ) single crystal electrolyte below a La0.6Sr0.4CoO3−δ (LSC) electrode. We observe yttrium segregation toward the YSZ/LSC electrolyte/electrode interface under reducing conditions. Under oxidizing conditions, the interface becomes Y depleted. The yttrium segregation is corroborated by an enhanced outward relaxation of the YSZ interfacial metal ion layer. At the same time, an increase in point defect concentration in the electrolyte at the interface was observed, as evidenced by reduced YSZ crystallographic site occupancies for the cations as well as the oxygen ions. Such changes in composition are expected to strongly influence the oxygen ion transport through this interface which plays an important role for the performance of solid oxide fuel cells. The structure of the interface is compared to the bare YSZ(100) surface structure near the microelectrode under identical conditions and to the structure of the YSZ(100) surface prepared under ultrahigh vacuum conditions. PMID:27346923

Emergent Interfacial Ferromagnetism in CaMnO3-based Superlattices

NASA Astrophysics Data System (ADS)

Grutter, Alexander

2014-03-01

Interfaces of complex oxide materials provide a rich playground not only for the exploration of properties not found in the bulk constituents but also for the development of functional interfaces to be incorporated in spintronic applications. Emergent interfacial magnetic phenomena have been of great interest but surprisingly there have been few examples of emergent interfacial ferromagnetism. In this talk, I will describe our recent work on the stabilization of ferromagnetism in CaMnO3-based superlattices. We have demonstrated ferromagnetism at the interface between the antiferromagnetic insulator CaMnO3 and a paramagnetic metallic layer, including CaRuO3 and LaNiO3. Theoretically the ferromagnetism has been attributed to an interfacial double exchange interaction among the interfacial Mn ions that is mediated by itinerant electrons from the paramagnetic metallic layer. Through polarized neutron reflectivity and observation of exchange bias, we have demonstrated that the ferromagnetism comes from Mn ions in a single unit cell at the interfaces just as theory has predicted. We have also demonstrated that the metallicity of the paramagnetic layer is critical in stabilizing ferromagnetism at the interface and that the interfacial ferromagnetism can be suppressed by suppressing the metallicity of the paramagnetic layer. Despite the agreement with theory, there remain open questions as to the magnetic interactions among the interfacial ferromagnetic layers. For example, the saturated magnetic moment modulates as a function of the thickness of both the CaMnO3 and paramagnetic metal layers. The origins of this oscillation are not well understood and may stem from either structural effects or long-range oscillatory magnetic coupling interactions reminiscent of RKKY interactions. Evidence of the doubling of the unit cell and long range antiferromagnetic correlations support these speculations. This work was supported by the U.S. Department of Energy, Office of Science, Division of Materials Sciences and Engineering, under Contract # DE-AC05-76RL01830 and DE-SC0008505.

Effects of image charges, interfacial charge discreteness, and surface roughness on the zeta potential of spherical electric double layers.

PubMed

Gan, Zecheng; Xing, Xiangjun; Xu, Zhenli

2012-07-21

We investigate the effects of image charges, interfacial charge discreteness, and surface roughness on spherical electric double layer structures in electrolyte solutions with divalent counterions in the setting of the primitive model. By using Monte Carlo simulations and the image charge method, the zeta potential profile and the integrated charge distribution function are computed for varying surface charge strengths and salt concentrations. Systematic comparisons were carried out between three distinct models for interfacial charges: (1) SURF1 with uniform surface charges, (2) SURF2 with discrete point charges on the interface, and (3) SURF3 with discrete interfacial charges and finite excluded volume. By comparing the integrated charge distribution function and the zeta potential profile, we argue that the potential at the distance of one ion diameter from the macroion surface is a suitable location to define the zeta potential. In SURF2 model, we find that image charge effects strongly enhance charge inversion for monovalent interfacial charges, and strongly suppress charge inversion for multivalent interfacial charges. For SURF3, the image charge effect becomes much smaller. Finally, with image charges in action, we find that excluded volumes (in SURF3) suppress charge inversion for monovalent interfacial charges and enhance charge inversion for multivalent interfacial charges. Overall, our results demonstrate that all these aspects, i.e., image charges, interfacial charge discreteness, their excluding volumes, have significant impacts on zeta potentials of electric double layers.

Energy dispersive-EXAFS of Pd nucleation at a liquid/liquid interface

NASA Astrophysics Data System (ADS)

Chang, S.-Y.; Booth, S. G.; Uehara, A.; Mosselmans, J. F. W.; Cibin, G.; Pham, V.-T.; Nataf, L.; Dryfe, R. A. W.; Schroeder, S. L. M.

2016-05-01

Energy dispersive extended X-ray absorption fine structure (EDE) has been applied to Pd nanoparticle nucleation at a liquid/liquid interface under control over the interfacial potential and thereby the driving force for nucleation. Preliminary analysis focusing on Pd K edge-step height determination shows that under supersaturated conditions the concentration of Pd near the interface fluctuate over a period of several hours, likely due to the continuous formation and dissolution of sub-critical nuclei. Open circuit potential measurements conducted ex-situ in a liquid/liquid electrochemical cell support this view, showing that the fluctuations in Pd concentration are also visible as variations in potential across the liquid/liquid interface. By decreasing the interfacial potential through inclusion of a common ion (tetraethylammonium, TEA+) the Pd nanoparticle growth rate could be slowed down, resulting in a smooth nucleation process. Eventually, when the TEA+ ions reached an equilibrium potential, Pd nucleation and particle growth were inhibited.

Towards a lattice-matching solid-state battery: synthesis of a new class of lithium-ion conductors with the spinel structure.

PubMed

Rosciano, Fabio; Pescarmona, Paolo P; Houthoofd, Kristof; Persoons, Andre; Bottke, Patrick; Wilkening, Martin

2013-04-28

Lithium ion batteries have conquered most of the portable electronics market and are now on the verge of deployment in large scale applications. To be competitive in the automotive and stationary sectors, however, they must be improved in the fields of safety and energy density (W h L(-1)). Solid-state batteries with a ceramic electrolyte offer the necessary advantages to significantly improve the current state-of-the-art technology. The major limit towards realizing a practical solid-state lithium-ion battery lies in the lack of viable ceramic ionic conductors. Only a few candidate materials are available, each carrying a difficult balance between advantages and drawbacks. Here we introduce a new class of possible solid-state lithium-ion conductors with the spinel structure. Such compounds could be coupled with spinel-type electrode materials to obtain a "lattice matching" solid device where low interfacial resistance could be achieved. Powders were prepared by wet chemistry, their structure was studied by means of diffraction techniques and magic angle spinning NMR, and Li(+) self-diffusion was estimated by static NMR line shape measurements. Profound differences in the Li(+) diffusion properties were observed depending on the composition, lithium content and cationic distribution. Local Li(+) hopping in the spinel materials is accompanied by a low activation energy of circa 0.35 eV being comparable with that of, e.g., LLZO-type garnets, which represent the current benchmark in this field. We propose these novel materials as a building block for a lattice-matching all-spinel solid-state battery with low interfacial resistance.

Insights into hydrogen bond dynamics at the interface of the charged monolayer-protected Au nanoparticle from molecular dynamics simulation.

PubMed

Li, Yunzhi; Yang, Zhen; Hu, Na; Zhou, Rongfei; Chen, Xiangshu

2013-05-14

The structure and dynamics properties of water molecules at the interface of the charged monolayer-protected Au nanoparticle (MPAN) have been investigated in detail by using classical molecular dynamics simulation. The simulation results demonstrated clearly that a well-defined hydration layer is formed at the interface of MPAN and a stable "ion wall" consisting of terminal NH3 (+) groups and Cl(-) counterions exists at the outmost region of self-assembled monolayer (SAM) where the translational and rotational motions of water molecules slow considerably down compared to those in the bulk owing to the presence of SAM and ion wall. Furthermore, we found that the translational motions of interfacial water molecules display a subdiffusive behavior while their rotational motions exhibit a nonexponential feature. The unique behavior of interfacial water molecules around the MPAN can be attributed to the interfacial hydrogen bond (HB) dynamics. By comparison, the lifetime of NH3 (+)-Cl(-) HBs was found to be the longest, favoring the stability of ion wall. Meanwhile, the lifetime of H2O-H2O HBs shows an obvious increase when the water molecules approach the Au core, suggesting the enhanced H2O-H2O HBs around the charged MPAN, which is contrary to the weaken H2O-H2O HBs around the neutral MPAN. Moreover, the HB lifetimes between water molecules and the ion wall (i.e., the Cl(-)-H2O and NH3 (+)-H2O HBs) are much longer than that of interfacial H2O-H2O HBs, which leads to the increasing rotational relaxation time and residence time of water molecules surrounding the ion wall. In addition, the corresponding binding energies for different HB types obtained from the precise density functional theory are in excellent accordance with above simulation results. The detailed HB dynamics studied in this work provides insights into the unique behavior of water molecules at the interface of charged self-assemblies of nanoparticles as well as proteins.

Molecular-Scale Investigation of Heavy Metal Ions at a Charged Langmuir Monolayer

NASA Astrophysics Data System (ADS)

Rock, William; Qiao, Baofu; Uysal, Ahmet; Bu, Wei; Lin, Binhua

Solvent extraction - the surfactant-aided preferential transfer of a species from an aqueous to an organic phase - is an important technique used in heavy and precious metal refining and reprocessing. Solvent extraction requires transfer through an oil/water interface, and interfacial interactions are expected to control transfer kinetics and phase stability, yet these key interactions are poorly understood. Langmuir monolayers with charged headgroups atop concentrated salt solutions containing heavy metal ions act as a model of solvent extraction interfaces; studies of ions at a charged surface are also fundamentally important to many other phenomena including protein solvation, mineral surface chemistry, and electrochemistry. We probe these charged interfaces using a variety of surface-sensitive techniques - vibrational sum frequency generation (VSFG) spectroscopy, x-ray reflectivity (XRR), x-ray fluorescence near total reflection (XFNTR), and grazing incidence diffraction (GID). We integrate experiments with Molecular Dynamics (MD) simulations to uncover the molecular-level interfacial structure. This work is supported by the U.S. DOE, BES, Contract DE-AC02-06CH11357. ChemMatCARS is supported by NSF/CHE-1346572.

First principles study on electrochemical and chemical stability of solid electrolyte–electrode interfaces in all-solid-state Li-ion batteries

DOE PAGES

Zhu, Yizhou; He, Xingfeng; Mo, Yifei

2015-12-11

All-solid-state Li-ion batteries based on ceramic solid electrolyte materials are a promising next-generation energy storage technology with high energy density and enhanced cycle life. The poor interfacial conductance is one of the key limitations in enabling all-solid-state Li-ion batteries. However, the origin of this poor conductance has not been understood, and there is limited knowledge about the solid electrolyte–electrode interfaces in all-solid-state Li-ion batteries. In this paper, we performed first principles calculations to evaluate the thermodynamics of the interfaces between solid electrolyte and electrode materials and to identify the chemical and electrochemical stabilities of these interfaces. Our computation results revealmore » that many solid electrolyte–electrode interfaces have limited chemical and electrochemical stability, and that the formation of interphase layers is thermodynamically favorable at these interfaces. These formed interphase layers with different properties significantly affect the electrochemical performance of all-solid-state Li-ion batteries. The mechanisms of applying interfacial coating layers to stabilize the interface and to reduce interfacial resistance are illustrated by our computation. This study demonstrates a computational scheme to evaluate the chemical and electrochemical stability of heterogeneous solid interfaces. Finally, the enhanced understanding of the interfacial phenomena provides the strategies of interface engineering to improve performances of all-solid-state Li-ion batteries.« less

Effect of ionization on the oxidation kinetics of aluminum nanoparticles

NASA Astrophysics Data System (ADS)

Zheng, Yao-Ting; He, Min; Cheng, Guang-xu; Zhang, Zaoxiao; Xuan, Fu-Zhen; Wang, Zhengdong

2018-03-01

Molecular dynamics simulation (MD) of the observed stepwise oxidation of core-shell structured Al/Al2O3 nanoparticles is presented. Different from the metal ion hopping process in the Cabrera-Mott model, which is assumed to occur only at a certain distance from the oxide layer, the MD simulation shows that Al atoms jump over various interfacial gaps directly under the thermal driving force. The energy barrier for Al ionization is found to be increased along with the enlargement of interfacial gap. A mechanism of competition between thermal driving force and ionization potential barrier is proposed in the interpretation of stepwise oxidation behavior.

Solar-Pumping Upconversion of Interfacial Coordination Nanoparticles.

PubMed

Ishii, Ayumi; Hasegawa, Miki

2017-01-30

An interfacial coordination nanoparticle successfully exhibited an upconversion blue emission excited by very low-power light irradiation, such as sunlight. The interfacial complex was composed of Yb ions and indigo dye, which formed a nano-ordered thin shell layer on a Tm 2 O 3 nanoparticle. At the surface of the Tm 2 O 3 particle, the indigo dye can be excited by non-laser excitation at 640 nm, following the intramolecular energy transfer from the indigo dye to the Yb ions. Additionally, the excitation energy of the Yb ion was upconverted to the blue emission of the Tm ion at 475 nm. This upconversion blue emission was achieved by excitation with a CW Xe lamp at an excitation power of 0.14 mW/cm 2 , which is significantly lower than the solar irradiation power of 1.4 mW/cm 2 at 640 ± 5 nm.

Metal-dielectric interactions

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1979-01-01

Metal direlectric surface interactions and dielectric films on metal substrates were investigated. Since interfacial interaction depends so heavily on the nature of the surfaces, analytical surface tools such as Auger emission spectroscopy, X-ray photoelectron spectroscopy and field ion microscopy were used to assist in surface and interfacial characterization. The results indicate that with metals contacting certain glasses in the clean state interfacial, bonding produces fractures in the glasses while when a film such as water is present, fractures occur in the metal near the interface. Friction forces were used to measure the interfacial bond strengths. Studies with metals contacting polymers using field ion microscopy revealed that strong bonding forces could develop being between a metal and polymer surface with polymer transferring to the metal surface in various ways depending upon the forces applied to the surface in contact. With the deposition of refractory carbides, silicides and borides onto metal and alloy substrates the presence of oxides at the interface or active gases in the deposition plasma were shown to alter interfacial properties and chemistry. Auger ion depth profile analysis indicated the chemical composition at the interface and this could be related to the mechanical, friction, and wear behavior of the coating.

Engineering three-dimensionally electrodeposited Si-on-Ni inverse opal structure for high volumetric capacity Li-ion microbattery anode.

PubMed

Liu, Hao; Cho, Hyung-Man; Meng, Ying Shirley; Li, Quan

2014-06-25

Aiming at improving the volumetric capacity of nanostructured Li-ion battery anode, an electrodeposited Si-on-Ni inverse opal structure has been proposed in the present work. This type of electrode provides three-dimensional bi-continuous pathways for ion/electron transport and high surface area-to-volume ratios, and thus exhibits lower interfacial resistance, but higher effective Li ions diffusion coefficients, when compared to the Si-on-Ni nanocable array electrode of the same active material mass. As a result, improved volumetric capacities and rate capabilities have been demonstrated in the Si-on-Ni inverse opal anode. We also show that optimization of the volumetric capacities and the rate performance of the inverse opal electrode can be realized by manipulating the pore size of the Ni scaffold and the thickness of the Si deposit.

Time Resolved Studies of Interfacial Reactions of Ozone with Pulmonary Phospholipid Surfactants Using Field Induced Droplet Ionization Mass Spectrometry

PubMed Central

Kim, Hugh I.; Kim, Hyungjun; Shin, Young Shik; Beegle, Luther W.; Goddard, William A.; Heath, James R.; Kanik, Isik; Beauchamp, J. L.

2013-01-01

Field induced droplet ionization mass spectrometry (FIDI-MS) comprises a soft ionization method to sample ions from the surface of microliter droplets. A pulsed electric field stretches neutral droplets until they develop dual Taylor cones, emitting streams of positively and negatively charged submicrometer droplets in opposite directions, with the desired polarity being directed into a mass spectrometer for analysis. This methodology is employed to study the heterogeneous ozonolysis of 1-palmitoyl-2-oleoyl-sn-phosphatidylglycerol (POPG) at the air–liquid interface in negative ion mode using FIDI mass spectrometry. Our results demonstrate unique characteristics of the heterogeneous reactions at the air–liquid interface. We observe the hydroxyhydroperoxide and the secondary ozonide as major products of POPG ozonolysis in the FIDI-MS spectra. These products are metastable and difficult to observe in the bulk phase, using standard electrospray ionization (ESI) for mass spectrometric analysis. We also present studies of the heterogeneous ozonolysis of a mixture of saturated and unsaturated phospholipids at the air–liquid interface. A mixture of the saturated phospholipid 1,2-dipalmitoyl-sn-phosphatidylglycerol (DPPG) and unsaturated POPG is investigated in negative ion mode using FIDI-MS while a mixture of 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) and 1-stearoyl-2-oleoyl-sn-phosphatidylcholine (SOPC) surfactant is studied in positive ion mode. In both cases FIDI-MS shows the saturated and unsaturated pulmonary surfactants form a mixed interfacial layer. Only the unsaturated phospholipid reacts with ozone, forming products that are more hydrophilic than the saturated phospholipid. With extensive ozonolysis only the saturated phospholipid remains at the droplet surface. Combining these experimental observations with the results of computational analysis provides an improved understanding of the interfacial structure and chemistry of a surfactant layer system when subject to oxidative stress. PMID:20608690

Adaptable silicon-carbon nanocables sandwiched between reduced graphene oxide sheets as lithium ion battery anodes.

PubMed

Wang, Bin; Li, Xianglong; Zhang, Xianfeng; Luo, Bin; Jin, Meihua; Liang, Minghui; Dayeh, Shadi A; Picraux, S T; Zhi, Linjie

2013-02-26

Silicon has been touted as one of the most promising anode materials for next generation lithium ion batteries. Yet, how to build energetic silicon-based electrode architectures by addressing the structural and interfacial stability issues facing silicon anodes still remains a big challenge. Here, we develop a novel kind of self-supporting binder-free silicon-based anodes via the encapsulation of silicon nanowires (SiNWs) with dual adaptable apparels (overlapped graphene (G) sheaths and reduced graphene oxide (RGO) overcoats). In the resulted architecture (namely, SiNW@G@RGO), the overlapped graphene sheets, as adaptable but sealed sheaths, prevent the direct exposure of encapsulated silicon to the electrolyte and enable the structural and interfacial stabilization of silicon nanowires. Meanwhile, the flexible and conductive RGO overcoats accommodate the volume change of embedded SiNW@G nanocables and thus maintain the structural and electrical integrity of the SiNW@G@RGO. As a result, the SiNW@G@RGO electrodes exhibit high reversible specific capacity of 1600 mAh g⁻¹ at 2.1 A g⁻¹, 80% capacity retention after 100 cycles, and superior rate capability (500 mAh g⁻¹ at 8.4 A g⁻¹) on the basis of the total electrode weight.

Unravelling surface and interfacial structures of a metal-organic framework by transmission electron microscopy.

PubMed

Zhu, Yihan; Ciston, Jim; Zheng, Bin; Miao, Xiaohe; Czarnik, Cory; Pan, Yichang; Sougrat, Rachid; Lai, Zhiping; Hsiung, Chia-En; Yao, Kexin; Pinnau, Ingo; Pan, Ming; Han, Yu

2017-05-01

Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosity and functionality, having promising applications in gas storage and separation, ion conduction and catalysis. It is challenging to observe MOFs with transmission electron microscopy (TEM) due to the extreme instability of MOFs upon electron beam irradiation. Here, we use a direct-detection electron-counting camera to acquire TEM images of the MOF ZIF-8 with an ultralow dose of 4.1 electrons per square ångström to retain the structural integrity. The obtained image involves structural information transferred up to 2.1 Å, allowing the resolution of individual atomic columns of Zn and organic linkers in the framework. Furthermore, TEM reveals important local structural features of ZIF-8 crystals that cannot be identified by diffraction techniques, including armchair-type surface terminations and coherent interfaces between assembled crystals. These observations allow us to understand how ZIF-8 crystals self-assemble and the subsequent influence of interfacial cavities on mass transport of guest molecules.

Unravelling surface and interfacial structures of a metal-organic framework by transmission electron microscopy

NASA Astrophysics Data System (ADS)

Zhu, Yihan; Ciston, Jim; Zheng, Bin; Miao, Xiaohe; Czarnik, Cory; Pan, Yichang; Sougrat, Rachid; Lai, Zhiping; Hsiung, Chia-En; Yao, Kexin; Pinnau, Ingo; Pan, Ming; Han, Yu

2017-05-01

Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosity and functionality, having promising applications in gas storage and separation, ion conduction and catalysis. It is challenging to observe MOFs with transmission electron microscopy (TEM) due to the extreme instability of MOFs upon electron beam irradiation. Here, we use a direct-detection electron-counting camera to acquire TEM images of the MOF ZIF-8 with an ultralow dose of 4.1 electrons per square ångström to retain the structural integrity. The obtained image involves structural information transferred up to 2.1 Å, allowing the resolution of individual atomic columns of Zn and organic linkers in the framework. Furthermore, TEM reveals important local structural features of ZIF-8 crystals that cannot be identified by diffraction techniques, including armchair-type surface terminations and coherent interfaces between assembled crystals. These observations allow us to understand how ZIF-8 crystals self-assemble and the subsequent influence of interfacial cavities on mass transport of guest molecules.

Electrode-Electrolyte Interfaces in Lithium-Sulfur Batteries with Liquid or Inorganic Solid Electrolytes.

PubMed

Yu, Xingwen; Manthiram, Arumugam

2017-11-21

Electrode-electrolyte interfacial properties play a vital role in the cycling performance of lithium-sulfur (Li-S) batteries. The issues at an electrode-electrolyte interface include electrochemical and chemical reactions occurring at the interface, formation mechanism of interfacial layers, compositional/structural characteristics of the interfacial layers, ionic transport across the interface, and thermodynamic and kinetic behaviors at the interface. Understanding the above critical issues is paramount for the development of strategies to enhance the overall performance of Li-S batteries. Liquid electrolytes commonly used in Li-S batteries bear resemblance to those employed in traditional lithium-ion batteries, which are generally composed of a lithium salt dissolved in a solvent matrix. However, due to a series of unique features associated with sulfur or polysulfides, ether-based solvents are generally employed in Li-S batteries rather than simply adopting the carbonate-type solvents that are generally used in the traditional Li + -ion batteries. In addition, the electrolytes of Li-S batteries usually comprise an important additive, LiNO 3 . The unique electrolyte components of Li-S batteries do not allow us to directly take the interfacial theories of the traditional Li + -ion batteries and apply them to Li-S batteries. On the other hand, during charging/discharging a Li-S battery, the dissolved polysulfide species migrate through the battery separator and react with the Li anode, which magnifies the complexity of the interfacial problems of Li-S batteries. However, current Li-S battery development paths have primarily been energized by advances in sulfur cathodes. Insight into the electrode-electrolyte interfacial behaviors has relatively been overshadowed. In this Account, we first examine the state-of-the-art contributions in understanding the solid-electrolyte interphase (SEI) formed on the Li-metal anode and sulfur cathode in conventional liquid-electrolyte Li-S batteries and how the resulting chemical and physical properties of the SEI affect the overall battery performance. A few strategies recently proposed for improving the stability of SEI are briefly summarized. Solid Li + -ion conductive electrolytes have been attempted for the development of Li-S batteries to eliminate the polysulfide shuttle issues. One approach is based on a concept of "all-solid-state Li-S battery," in which all the cell components are in the solid state. Another approach is based on a "hybrid-electrolyte Li-S battery" concept, in which the solid electrolyte plays roles both as a Li + -ion conductor for the electrochemical reaction and as a separator to prevent polysulfide shuttle. However, these endeavors with the solid electrolyte are not able to provide an overall satisfactory cell performance. In addition to the low ionic conductivity of solid-state electrolytes, a critical issue lies in the poor interfacial properties between the electrode and the solid electrolyte. This Account provides a survey of the relevant research progress in understanding and manipulating the interfaces of electrode and solid electrolytes in both the "all-solid-state Li-S batteries" and the "hybrid-electrolyte Li-S batteries". A recently proposed "semi-solid-state Li-S battery" concept is also briefly discussed. Finally, future research and development directions in all the above areas are suggested.

Interfacial reactions of ozone with surfactant protein B in a model lung surfactant system.

PubMed

Kim, Hugh I; Kim, Hyungjun; Shin, Young Shik; Beegle, Luther W; Jang, Seung Soon; Neidholdt, Evan L; Goddard, William A; Heath, James R; Kanik, Isik; Beauchamp, J L

2010-02-24

Oxidative stresses from irritants such as hydrogen peroxide and ozone (O(3)) can cause dysfunction of the pulmonary surfactant (PS) layer in the human lung, resulting in chronic diseases of the respiratory tract. For identification of structural changes of pulmonary surfactant protein B (SP-B) due to the heterogeneous reaction with O(3), field-induced droplet ionization (FIDI) mass spectrometry has been utilized. FIDI is a soft ionization method in which ions are extracted from the surface of microliter-volume droplets. We report structurally specific oxidative changes of SP-B(1-25) (a shortened version of human SP-B) at the air-liquid interface. We also present studies of the interfacial oxidation of SP-B(1-25) in a nonionizable 1-palmitoyl-2-oleoyl-sn-glycerol (POG) surfactant layer as a model PS system, where competitive oxidation of the two components is observed. Our results indicate that the heterogeneous reaction of SP-B(1-25) at the interface is quite different from that in the solution phase. In comparison with the nearly complete homogeneous oxidation of SP-B(1-25), only a subset of the amino acids known to react with ozone are oxidized by direct ozonolysis in the hydrophobic interfacial environment, both with and without the lipid surfactant layer. Combining these experimental observations with the results of molecular dynamics simulations provides an improved understanding of the interfacial structure and chemistry of a model lung surfactant system subjected to oxidative stress.

Metal ion interaction with phosphorylated tyrosine analogue monolayers on gold.

PubMed

Petoral, Rodrigo M; Björefors, Fredrik; Uvdal, Kajsa

2006-11-23

Phosphorylated tyrosine analogue molecules (pTyr-PT) were assembled onto gold substrates, and the resulting monolayers were used for metal ion interaction studies. The monolayers were characterized by X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRAS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), both prior to and after exposure to metal ions. XPS verified the elemental composition of the molecular adsorbate and the presence of metal ions coordinated to the phosphate groups. Both the angle-dependent XPS and IRAS results were consistent with the change in the structural orientation of the pTyr-PT monolayer upon exposure to metal ions. The differential capacitance of the monolayers upon coordination of the metal ions was evaluated using EIS. These metal ions were found to significantly change the capacitance of the pTyr-PT monolayers in contrast to the nonphosphorylated tyrosine analogue (TPT). CV results showed reduced electrochemical blocking capabilities of the phosphorylated analogue monolayer when exposed to metal ions, supporting the change in the structure of the monolayer observed by XPS and IRAS. The largest change in the structure and interfacial capacitance was observed for aluminum ions, compared to calcium, magnesium, and chromium ions. This type of monolayer shows an excellent capability to coordinate metal ions and has a high potential for use as sensing layers in biochip applications to monitor the presence of metal ions.

Interfacial development of electrophoretically deposited graphene oxide films on Al alloys

DOE PAGES

Jin, Sumin; Dickerson, James H.; Pham, Viet Hung; ...

2015-07-28

Adhesion between film and substrate is critical for electronic device and coating applications. Interfacial development between electrophoretically deposited graphene oxide films on Al 1100 and Al 5052 alloys were investigated using FT-IR and XPS depth profiling techniques. Obtained results suggest metal ion permeation from the substrates into deposited graphene oxide films. The interface between the films and the substrates were primarily composed of Al-O-C bonds from oxygenated defects on graphene oxide plane rather than expected Al-C formation. Films heat treated at 150 °C had change in microstructure and peak shifts in XPS spectra suggesting change in chemical structure of bondsmore » between the films and the substrates.« less

Metal-semiconductor interfacial reactions - Ni/Si system

NASA Technical Reports Server (NTRS)

Cheung, N. W.; Grunthaner, P. J.; Grunthaner, F. J.; Mayer, J. W.; Ullrich, B. M.

1981-01-01

X-ray photoelectron spectroscopy and channeling measurements with MeV He-4(+) ions have been used to probe the structure of the interface in the Ni/Si system. It is found that reactions occur where Ni is deposited on Si at 10 to the -10th torr: Si atoms are displaced from lattice sites, the Ni atoms are in an Si-rich environment, and the Ni/Si interface is graded in composition. Composition gradients are present at both interfaces in the Si/Ni2/Si/Ni system. For the Ni-Si system, cooling the substrate to 100 K slows down the reaction rate. The temperature dependence of the interfacial reactivity indicates the kinetic nature of metal-semiconductor interfaces.

Gas-liquid interface of room-temperature ionic liquids.

PubMed

Santos, Cherry S; Baldelli, Steven

2010-06-01

The organization of ions at the interface of ionic liquids and the vacuum is an ideal system to test new ideas and concepts on the interfacial chemistry of electrolyte systems in the limit of no solvent medium. Whilst electrolyte systems have numerous theoretical and experimental methods used to investigate their properties, the ionic liquids are relatively new and our understanding of the interfacial properties is just beginning to be explored. In this critical review, the gas-liquid interface is reviewed, as this interface does not depend on the preparation of another medium and thus produces a natural interface. The interface has been investigated by sum frequency generation vibrational spectroscopy and ultra-high vacuum techniques. The results provide a detailed molecular-level view of the surface composition and structure. These have been complemented by theoretical studies. The combinations of treatments on this interface are starting to provide a somewhat convergent description of how the ions are organized at this neat interface (108 references).

Interfacial micropore defect formation in PEDOT:PSS-Si hybrid solar cells probed by TOF-SIMS 3D chemical imaging.

PubMed

Thomas, Joseph P; Zhao, Liyan; Abd-Ellah, Marwa; Heinig, Nina F; Leung, K T

2013-07-16

Conducting p-type polymer layers on n-type Si have been widely studied for the fabrication of cost-effective hybrid solar cells. In this work, time-of-flight secondary ion mass spectrometry (TOF-SIMS) is used to provide three-dimensional chemical imaging of the interface between poly(3,4-ethylene-dioxythiophene):polystyrenesulfonate (PEDOT:PSS) and SiOx/Si in a hybrid solar cell. To minimize structural damage to the polymer layer, an Ar cluster sputtering source is used for depth profiling. The present result shows the formation of micropore defects in the interface region of the PEDOT:PSS layer on the SiOx/Si substrate. This interfacial micropore defect formation becomes more prominent with increasing thickness of the native oxide layer, which is a key device parameter that greatly affects the hybrid solar cell performance. Three-dimensional chemical imaging coupled with Ar cluster ion sputtering has therefore been demonstrated as an emerging technique for probing the interface of this and other polymer-inorganic systems.

Halide Ions Effects on Surface Excess of Long Chain Ionic Liquids Water Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wenjie; Sung, Woongmo; Ao, Mingqi

2013-10-07

The interfacial structure and composition of water solutions with alkylimidazolium ionic liquids varying in their halide anions ([C12mim][X], X = Cl and I) were investigated by X-ray near-total-reflection fluorescence spectroscopy and X-ray reflectivity measurements. We demonstrate that X-ray fluorescence and reflectivity techniques provide a more direct measurement of surface adsorption. Furthermore, we show that for [C12mim][Cl] and [C12mim][I] solutions with mixed inorganic salts (NaI, NaCl), I– ions replace Cl– above the critical micelle concentration (CMC) of [C12mim][Cl] at much lower concentrations of NaI, whereas NaCl concentrations a hundred times higher than the CMC of [C12mim][I] only partially replace the I–more » at the interface. Our surface-sensitive X-ray diffraction and spectroscopy provide two independent tools to directly determine the surface adsorption of ionic surfactants and the interfacial composition of the surface films.« less

Determination of Halide Concentrations at the Interface of Zwitterionic Micelles by Chemical Trapping: Influence of the Orientation of the Dipole and the Nature of the Cation.

PubMed

Cuccovia; Romsted; Chaimovich

1999-12-01

The interfacial concentrations of Cl(-) and Br(-) in aqueous zwitterionic micelles were determined by chemical trapping by analyzing product yields from spontaneous dediazoniation of micelle-bound 2,6-dimethyl-4-hexadecylbenzenediazonium ion. Interfacial concentrations of Cl(-) and Br(-) in 3-(N-hexadecyl-N, N-dimethylammonio) propane sulfonate, HPS, micelles were higher than in bulk solutions prepared with Li(+), Na(+), Rb(+), Cs(+), tetramethylammonium (TMA(+)), Mg(+2), and Ca(+2) salts. In contrast, the interfacial concentrations of Cl(-) and Br(-) were generally lower than in bulk solution in hexadecylphosphoryl choline, HDPC, micelles for all salts except Mg(+2) and Ca(+2). In both HPS and HDPC micelles the interfacial concentration of Br(-) was higher than that of Cl(-), showing that binding is anion selective. The cation had a large effect on the interfacial concentration of halide ions with HDPC micelles decreasing in the order Ca(2+) > Mg(2+) > Li(+) > Na(+) > K(+) > Cs(+) > Rb(+) > TMA(+). These results are the first direct and extensive determination of local halide ion concentration at the surface of zwitterionic micelles, and they demonstrate that chemical trapping methodology will work in membranes at physiologically relevant salt concentrations. Copyright 1999 Academic Press.

Mechanistic study of the rubber-brass adhesion interphase

NASA Astrophysics Data System (ADS)

Ashirgade, Akshay

Brass-plated steel tire cords form an essential strengthening component of a radial automobile tire. Adhesion between rubber compound and brass-plated steel tire cord is crucial in governing the overall performance of tires. The rubber-brass interfacial adhesion is influenced by the chemical composition and thickness of the interfacial layer. It has been shown that the interfacial layer consists mainly of sulfides and oxides of copper and zinc. This thesis discusses the effect of changes in the chemical composition and the structure of the interfacial layers due to addition of adhesion promoter resins. Grazing incidence X-Ray Diffraction (GIXRD) experiments were run on sulfidized polished brass coupons previously bonded to six experimental rubber compounds. It was confirmed that heat and humidity conditions lead to physical and chemical changes of the rubber-steel tire cord interfacial layer, closely related to the degree of rubber-brass adhesion. Morphological transformation of the interfacial layer led to loss of adhesion after aging. The adhesion promoter resins inhibit unfavorable morphological changes in the interfacial layer thus stabilizing it during aging and prolonging failure. Tire cord adhesion tests illustrated that the one-component resins improved adhesion after aging using a rubber compound with lower cobalt loading. Based on the acquired diffraction profiles, these resins were also found to impede crystallization of the sulfide layer after aging leading to improved adhesion. Secondary Ion Mass Spectrometry (SIMS) depth profiles, SEM micrographs and AFM images strongly corroborated the findings from GIXRD. FTIR was utilized in a novel way to understand the degradation mechanism due to aging. A model for rubber and interfacial layer degradation is proposed to illustrate the effect of aging and the one-component resins. This interfacial analysis adds valuable new information to our understanding of the complex nature of the rubber-brass bonding mechanism.

Heat transfer enhancement in a lithium-ion cell through improved material-level thermal transport

NASA Astrophysics Data System (ADS)

Vishwakarma, Vivek; Waghela, Chirag; Wei, Zi; Prasher, Ravi; Nagpure, Shrikant C.; Li, Jianlin; Liu, Fuqiang; Daniel, Claus; Jain, Ankur

2015-12-01

While Li-ion cells offer excellent electrochemical performance for several applications including electric vehicles, they also exhibit poor thermal transport characteristics, resulting in reduced performance, overheating and thermal runaway. Inadequate heat removal from Li-ion cells originates from poor thermal conductivity within the cell. This paper identifies the rate-limiting material-level process that dominates overall thermal conduction in a Li-ion cell. Results indicate that thermal characteristics of a Li-ion cell are largely dominated by heat transfer across the cathode-separator interface rather than heat transfer through the materials themselves. This interfacial thermal resistance contributes around 88% of total thermal resistance in the cell. Measured value of interfacial resistance is close to that obtained from theoretical models that account for weak adhesion and large acoustic mismatch between cathode and separator. Further, to address this problem, an amine-based chemical bridging of the interface is carried out. This is shown to result in in four-times lower interfacial thermal resistance without deterioration in electrochemical performance, thereby increasing effective thermal conductivity by three-fold. This improvement is expected to reduce peak temperature rise during operation by 60%. By identifying and addressing the material-level root cause of poor thermal transport in Li-ion cells, this work may contributes towards improved thermal performance of Li-ion cells.

IR spectroscopy of protonation in benzene-water nanoclusters: hydronium, zundel, and eigen at a hydrophobic interface.

PubMed

Cheng, Timothy C; Bandyopadhyay, Biswajit; Mosley, Jonathan D; Duncan, Michael A

2012-08-08

The structure of ions in water at a hydrophobic interface influences important processes throughout chemistry and biology. However, experiments to measure these structures are limited by the distribution of configurations present and the inability to selectively probe the interfacial region. Here, protonated nanoclusters containing benzene and water are produced in the gas phase, size-selected, and investigated with infrared laser spectroscopy. Proton stretch, free OH, and hydrogen-bonding vibrations uniquely define protonation sites and hydrogen-bonding networks. The structures consist of protonated water clusters binding to the hydrophobic interface of neutral benzene via one or more π-hydrogen bonds. Comparison to the spectra of isolated hydronium, zundel, or eigen ions reveals the inductive effects and local ordering induced by the interface. The structures and interactions revealed here represent key features expected for aqueous hydrophobic interfaces.

Interfacial Engineered Polyaniline/Sulfur-Doped TiO2 Nanotube Arrays for Ultralong Cycle Lifetime Fiber-Shaped, Solid-State Supercapacitors.

PubMed

Li, Chun; Wang, Zhuanpei; Li, Shengwen; Cheng, Jianli; Zhang, Yanning; Zhou, Jingwen; Yang, Dan; Tong, Dong-Ge; Wang, Bin

2018-05-30

Fiber-shaped supercapacitors (FSCs) have great promises in wearable electronics applications. However, the limited specific surface area and inadequate structural stability caused by the weak interfacial interactions of the electrodes result in relatively low specific capacitance and unsatisfactory cycle lifetime. Herein, solid-state FSCs with high energy density and ultralong cycle lifetime based on polyaniline (PANI)/sulfur-doped TiO 2 nanotube arrays (PANI/S-TiO 2 ) are fabricated by interfacial engineering. The experimental results and ab initio calculations reveal that S doping can effectively promote the conductivity of titania nanotubes and increase the binding energy of PANI anchored on the electrode surface, leading to a much stronger binding of PANI on the surface of the electrode and excellent electrode structure stability. As a result, the FSCs using the PANI/S-TiO 2 electrodes deliver a high specific capacitance of 91.9 mF cm -2 , a capacitance retention of 93.78% after 12 000 charge-discharge cycles, and an areal energy density of 3.2 μW h cm -2 . Meanwhile, the all-solid-state FSC device retains its excellent flexibility and stable electrochemical capacitance even after bending 150 cycles. The enhanced performances of FSCs could be attributed to the large surface area, reduced ion diffusion path, improved electrical conductivity, and engineered interfacial interaction of the rationally designed electrodes.

pH-responsive ion transport in polyelectrolyte multilayers of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(4-styrenesulfonic acid-co-maleic acid) (PSS-MA) bearing strong- and weak anionic groups.

PubMed

Maza, Eliana; Tuninetti, Jimena S; Politakos, Nikolaos; Knoll, Wolfgang; Moya, Sergio; Azzaroni, Omar

2015-11-28

The layer-by-layer construction of interfacial architectures displaying stimuli-responsive control of mass transport is attracting increasing interest in materials science. In this work, we describe the creation of interfacial architectures displaying pH-dependent ionic transport properties which until now have not been observed in polyelectrolyte multilayers. We describe a novel approach to create pH-controlled ion-rectifying systems employing polyelectrolyte multilayers assembled from a copolymer containing both weakly and strongly charged pendant groups, poly(4-styrenesulfonic acid-co-maleic acid) (PSS-MA), alternately deposited with poly(diallyldimethylammonium chloride) (PDADMAC). The conceptual framework is based on the very contrasting and differential interactions of PSS and MA units with PDADMAC. In our setting, sulfonate groups play a structural role by conferring stability to the multilayer due to the strong electrostatic interactions with the polycations, while the weakly interacting MA groups remain "silent" within the film and then act as on-demand pH-responsive units. When these multilayers are combined with a strong cationic capping layer that repels the passage of cationic probes, a pH-gateable rectified transport of anions is observed. Concomitantly, we also observed that these functional properties are significantly affected when multilayers are subjected to extensive pH cycling as a consequence of irreversible morphological changes taking place in the film. We envision that the synergy derived from combining weak and strong interactions within the same multilayer will play a key role in the construction of new interfacial architectures displaying tailorable ion transport properties.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Gui -Liang; Amine, Rachid; Xu, Yue -Feng

Cathode materials are critical to the energy density, power density and safety of sodium-ion batteries (SIBs). Herein, we performed a comprehensive study to elucidate and exemplify the interplay mechanism between phase structures, interfacial microstrain and electrochemical properties of layered-structured Na xNi 1/3Co 1/3Mn 1/3O 2 cathode materials for high voltage SIBs. The electrochemical test results showed that Na xNi 1/3Co 1/3Mn 1/3O 2 with an intergrowth P2/O3/O1 structure demonstrates better electrochemical performance and better thermal stability than Na xNi 1/3Co 1/3Mn 1/3O 2 with P2/O3 binary-phase integration and Na xNi 1/3Co 1/3Mn 1/3O 2 where only the P phase ismore » dominant. This result is caused by the distinct interfacial microstrain development during the synthesis and cycling of the P2/O3/O1 phase. In operando high energy X-ray diffraction further revealed that the intergrowth P2/O1/O3 cathode can inhibit the irreversible P2–O2 phase transformation and simultaneously improve the structure stability of the O3 and O1 phases during cycling. Here, we believe that interfacial microstrain can serve as an indispensable bridge to guide future design and synthesis of high performance SIB cathode materials and other high energy battery materials.« less

Interfacial Li-ion localization in hierarchical carbon anodes

DOE PAGES

McNutt, Nicholas W.; Rios, Orlando; Maroulas, Vasileios; ...

2016-10-24

An understanding of the nanoscale structure and energetics of carbon composites is critical for their applications in electric energy storage. Here, we study the properties of carbon anodes synthesized from low-cost renewable lignin biopolymers for use in energy storage applications such as Li-ion batteries. The anodes possess both nanoscale and mesoscale order, consisting of carbon nanocrystallites distributed within an amorphous carbon matrix. Molecular dynamics simulations of an experimentally validated model of the anode is used to elucidate the nature of Li-ion storage. We report the discovery of a novel mechanism of Li-ion storage, one in which Li+ is not intercalatedmore » between layers of carbon (as is the case in graphitic anodes), but rather is localized at the interface of crystalline carbon domains. In particular, the effects of Li-ion binding energy on the Li-Li, Li-H, and Li-C pair distribution functions are revealed, along with the effect on charge distribution. As a result, the atomic environments surrounding the Li-ions are grouped on the basis of ion energy and then convolved into archetypal structural motifs that reveal deep insight into the geometry of ion localization in disordered systems.« less

Viewpoint 9--molecular structure of aqueous interfaces

NASA Technical Reports Server (NTRS)

Pohorille, A.; Wilson, M. A.

1993-01-01

In this review we summarize recent progress in our understanding of the structure of aqueous interfaces emerging from molecular level computer simulations. It is emphasized that the presence of the interface induces specific structural effects which, in turn, influence a wide variety of phenomena occurring near the phase boundaries. At the liquid-vapor interface, the most probable orientations of a water molecule is such that its dipole moment lies parallel to the interface, one O-H bond points toward the vapor and the other O-H bond is directed toward the liquid. The orientational distributions are broad and slightly asymmetric, resulting in an excess dipole moment pointing toward the liquid. These structural preferences persist at interfaces between water and nonpolar liquids, indicating that the interactions between the two liquids in contact are weak. It was found that liquid-liquid interfaces are locally sharp but broadened by capillary waves. One consequence of anisotropic orientations of interfacial water molecules is asymmetric interactions, with respect to the sign of the charge, of ions with the water surface. It was found that even very close to the surface ions retain their hydration shells. New features of aqueous interfaces have been revealed in studies of water-membrane and water-monolayer systems. In particular, water molecules are strongly oriented by the polar head groups of the amphiphilic phase, and they penetrate the hydrophilic head-group region, but not the hydrophobic core. At infinite dilution near interfaces, amphiphilic molecules exhibit behavior different from that in the gas phase or in bulk water. This result sheds new light on the nature of hydrophobic effect in the interfacial regions. The presence of interfaces was also shown to affect both equilibrium and dynamic components of rates of chemical reactions. Applications of continuum models to interfacial problems have been, so far, unsuccessful. This, again, underscores the importance of molecular-level information about interfaces.

Molecular dynamics study of structure and vibrational spectra at zwitterionoic lipid/aqueous KCl, NaCl, and CaCl2 solution interfaces

NASA Astrophysics Data System (ADS)

Ishiyama, Tatsuya; Shirai, Shinnosuke; Okumura, Tomoaki; Morita, Akihiro

2018-06-01

Molecular dynamics (MD) simulations of KCl, NaCl, and CaCl2 solution/dipalmytoylphosphatidylcholine lipid interfaces were performed to analyze heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectra in relation to the interfacial water structure. The present MD simulation well reproduces the experimental spectra and elucidates a specific cation effect on the interfacial structure. The K+, Na+, and Ca2+ cation species penetrate in the lipid layer more than the anions in this order, due to the electrostatic interaction with negative polar groups of lipid, and the electric double layer between the cations and anions cancels the intrinsic orientation of water at the water/lipid interface. These mechanisms explain the HD-VSFG spectrum of the water/lipid interface and its spectral perturbation by adding the ions. The lipid monolayer reverses the order of surface preference of the cations at the solution/lipid interface from that at the solution/air interface.

New faces of porous Prussian blue: interfacial assembly of integrated hetero-structures for sensing applications.

PubMed

Kong, Biao; Selomulya, Cordelia; Zheng, Gengfeng; Zhao, Dongyuan

2015-11-21

Prussian blue (PB), the oldest synthetic coordination compound, is a classic and fascinating transition metal coordination material. Prussian blue is based on a three-dimensional (3-D) cubic polymeric porous network consisting of alternating ferric and ferrous ions, which provides facile assembly as well as precise interaction with active sites at functional interfaces. A fundamental understanding of the assembly mechanism of PB hetero-interfaces is essential to enable the full potential applications of PB crystals, including chemical sensing, catalysis, gas storage, drug delivery and electronic displays. Developing controlled assembly methods towards functionally integrated hetero-interfaces with adjustable sizes and morphology of PB crystals is necessary. A key point in the functional interface and device integration of PB nanocrystals is the fabrication of hetero-interfaces in a well-defined and oriented fashion on given substrates. This review will bring together these key aspects of the hetero-interfaces of PB nanocrystals, ranging from structure and properties, interfacial assembly strategies, to integrated hetero-structures for diverse sensing.

Li-Ion Localization and Energetics as a Function of Anode Structure.

PubMed

McNutt, Nicholas W; McDonnell, Marshall; Rios, Orlando; Keffer, David J

2017-03-01

In this work, we study the effect of carbon composite anode structure on the localization and energetics of Li-ions. A computational molecular dynamics study is combined with experimental results from neutron scattering experiments to understand the effect of composite density, crystallite size, volume fraction of crystalline carbon, and ion loading on the nature of ion storage in novel, lignin-derived composite materials. In a recent work, we demonstrated that these carbon composites display a fundamentally different mechanism for Li-ion storage than traditional graphitic anodes. The edges of the crystalline and amorphous fragments of aromatic carbon that exist in these composites are terminated by hydrogen atoms, which play a crucial role in adsorption. In this work, we demonstrate how differences in composite structure due to changes in the processing conditions alter the type and extent of the interface between the amorphous and crystalline domains, thus impacting the nature of Li-ion storage. The effects of structural properties are evaluated using a suite of pair distribution functions as well as an original technique to extract archetypal structures, in the form of three-dimensional atomic density distributions, from highly disordered systems. The energetics of Li-ion binding are understood by relating changes in the energy and charge distributions to changes in structural properties. The distribution of Li-ion energies reveals that some structures lead to greater chemisorption, while others have greater physisorption. Carbon composites with a high volume fraction of small crystallites demonstrate the highest ion storage capacity because of the high interfacial area between the crystalline and amorphous domains. At these interfaces, stable H atoms, terminating the graphitic crystallites, provide favorable sites for reversible Li adsorption.

Interfacial concentrations of chloride and bromide in zwitterionic micelles with opposite dipoles: experimental determination by chemical trapping and a theoretical description.

PubMed

de Souza, Tereza Pereira; Chaimovich, Hernan; Fahr, Alfred; Schweitzer, Bianca; Agostinho Neto, Augusto; Cuccovia, Iolanda Midea

2012-04-01

Interfacial concentrations of chloride and bromide ions, with Li(+), Na(+), K(+), Rb(+), Cs(+), trimethylammonium (TMA(+)), Ca(2+), and Mg(2+) as counterions, were determined by chemical trapping in micelles formed by two zwitterionic surfactants, namely N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and hexadecylphosphorylcholine (HDPC) micelles. Appropriate standard curves for the chemical trapping method were obtained by measuring the product yields of chloride and bromide salts with 2,4,6-trimethyl-benzenediazonium (BF(4)) in the presence of low molecular analogs (N,N,N-trimethyl-propane sulfonate and methyl-phosphorylcholine) of the employed surfactants. The experimentally determined values for the local Br(-) (Cl(-)) concentrations were modeled by fully integrated non-linear Poisson Boltzmann equations. The best fits to all experimental data were obtained by considering that ions at the interface are not fixed at an adsorption site but are free to move in the interfacial plane. In addition, the calculation of ion distribution allowed the estimation of the degree of ion coverage by using standard chemical potential differences accounting for ion specificity. Copyright © 2012 Elsevier Inc. All rights reserved.

Quantitative analysis of total reflection X-ray fluorescence from finely layered structures using XeRay.

PubMed

Gong, Zhiliang; Kerr, Daniel; Hwang, Hyeondo Luke; Henderson, J Michael; Suwatthee, Tiffany; Slaw, Benjamin R; Cao, Kathleen D; Lin, Binhua; Bu, Wei; Lee, Ka Yee C

2017-03-01

Total reflection x-ray fluorescence (TXRF) is a widely applicable experimental technique for studying chemical element distributions across finely layered structures at extremely high sensitivity. To promote and facilitate scientific discovery using TXRF, we developed a MATLAB-based software package with a graphical user interface, named XeRay, for quick, accurate, and intuitive data analysis. XeRay lets the user model any layered system, each layer with its independent chemical composition and thickness, and enables fine-tuned data fitting. The accuracy of XeRay has been tested in the analysis of TXRF data from both air/liquid interface and liquid/liquid interfacial studies and has been compared to literature results. In an air/liquid interface study, Ca 2+ sequestration was measured at a Langmuir monolayer of 1-stearoyl-2-oleoyl-sn-glycero-3-phosphatidic acid (SOPA) on a buffer solution of 1 mM CaCl 2 at pH 7.5. Data analysis with XeRay reveals that each 1 nm 2 of interfacial area contains 2.38 ± 0.06 Ca 2+ ions, which corresponds to a 1:1 ratio between SOPA headgroups and Ca 2+ ions, consistent with several earlier reports. For the liquid/liquid interface study of Sr 2+ enrichment at the dodecane/surfactant/water interface, analysis using XeRay gives a surface enrichment of Sr 2+ at 68 -5 +6 Å 2 per ion, consistent with the result published for the same dataset.

Quantitative analysis of total reflection X-ray fluorescence from finely layered structures using XeRay

NASA Astrophysics Data System (ADS)

Gong, Zhiliang; Kerr, Daniel; Hwang, Hyeondo Luke; Henderson, J. Michael; Suwatthee, Tiffany; Slaw, Benjamin R.; Cao, Kathleen D.; Lin, Binhua; Bu, Wei; Lee, Ka Yee C.

2017-03-01

Total reflection x-ray fluorescence (TXRF) is a widely applicable experimental technique for studying chemical element distributions across finely layered structures at extremely high sensitivity. To promote and facilitate scientific discovery using TXRF, we developed a MATLAB-based software package with a graphical user interface, named XeRay, for quick, accurate, and intuitive data analysis. XeRay lets the user model any layered system, each layer with its independent chemical composition and thickness, and enables fine-tuned data fitting. The accuracy of XeRay has been tested in the analysis of TXRF data from both air/liquid interface and liquid/liquid interfacial studies and has been compared to literature results. In an air/liquid interface study, Ca2+ sequestration was measured at a Langmuir monolayer of 1-stearoyl-2-oleoyl-sn-glycero-3-phosphatidic acid (SOPA) on a buffer solution of 1 mM CaCl2 at pH 7.5. Data analysis with XeRay reveals that each 1 nm2 of interfacial area contains 2.38 ± 0.06 Ca2+ ions, which corresponds to a 1:1 ratio between SOPA headgroups and Ca2+ ions, consistent with several earlier reports. For the liquid/liquid interface study of Sr2+ enrichment at the dodecane/surfactant/water interface, analysis using XeRay gives a surface enrichment of Sr2+ at 68-5+6 Å2 per ion, consistent with the result published for the same dataset.

Quantitative analysis of total reflection X-ray fluorescence from finely layered structures using XeRay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Zhiliang; Kerr, Daniel; Hwang, Hyeondo Luke

Total reflection x-ray fluorescence (TXRF) is a widely applicable experimental technique for studying chemical element distributions across finely layered structures at extremely high sensitivity. To promote and facilitate scientific discovery using TXRF, we developed a MATLAB-based software package with a graphical user interface, named XeRay, for quick, accurate, and intuitive data analysis. XeRay lets the user model any layered system, each layer with its independent chemical composition and thickness, and enables fine-tuned data fitting. The accuracy of XeRay has been tested in the analysis of TXRF data from both air/liquid interface and liquid/liquid interfacial studies and has been compared tomore » literature results. In an air/liquid interface study, Ca2+ sequestration was measured at a Langmuir monolayer of 1-stearoyl-2-oleoyl-sn-glycero-3-phosphatidic acid (SOPA) on a buffer solution of 1 mM CaCl2 at pH 7.5. Data analysis with XeRay reveals that each 1 nm2 of interfacial area contains 2.38 ± 0.06 Ca2+ ions, which corresponds to a 1:1 ratio between SOPA headgroups and Ca2+ ions, consistent with several earlier reports. For the liquid/liquid interface study of Sr2+ enrichment at the dodecane/surfactant/water interface, analysis using XeRay gives a surface enrichment of Sr2+ at 68+6-568-5+6 Å2 per ion, consistent with the result published for the same dataset.« less

Gas-solid interfacial modification of oxygen activity in layered oxide cathodes for lithium-ion batteries.

PubMed

Qiu, Bao; Zhang, Minghao; Wu, Lijun; Wang, Jun; Xia, Yonggao; Qian, Danna; Liu, Haodong; Hy, Sunny; Chen, Yan; An, Ke; Zhu, Yimei; Liu, Zhaoping; Meng, Ying Shirley

2016-07-01

Lattice oxygen can play an intriguing role in electrochemical processes, not only maintaining structural stability, but also influencing electron and ion transport properties in high-capacity oxide cathode materials for Li-ion batteries. Here, we report the design of a gas-solid interface reaction to achieve delicate control of oxygen activity through uniformly creating oxygen vacancies without affecting structural integrity of Li-rich layered oxides. Theoretical calculations and experimental characterizations demonstrate that oxygen vacancies provide a favourable ionic diffusion environment in the bulk and significantly suppress gas release from the surface. The target material is achievable in delivering a discharge capacity as high as 301 mAh g(-1) with initial Coulombic efficiency of 93.2%. After 100 cycles, a reversible capacity of 300 mAh g(-1) still remains without any obvious decay in voltage. This study sheds light on the comprehensive design and control of oxygen activity in transition-metal-oxide systems for next-generation Li-ion batteries.

Gas–solid interfacial modification of oxygen activity in layered oxide cathodes for lithium-ion batteries

PubMed Central

Qiu, Bao; Zhang, Minghao; Wu, Lijun; Wang, Jun; Xia, Yonggao; Qian, Danna; Liu, Haodong; Hy, Sunny; Chen, Yan; An, Ke; Zhu, Yimei; Liu, Zhaoping; Meng, Ying Shirley

2016-01-01

Lattice oxygen can play an intriguing role in electrochemical processes, not only maintaining structural stability, but also influencing electron and ion transport properties in high-capacity oxide cathode materials for Li-ion batteries. Here, we report the design of a gas–solid interface reaction to achieve delicate control of oxygen activity through uniformly creating oxygen vacancies without affecting structural integrity of Li-rich layered oxides. Theoretical calculations and experimental characterizations demonstrate that oxygen vacancies provide a favourable ionic diffusion environment in the bulk and significantly suppress gas release from the surface. The target material is achievable in delivering a discharge capacity as high as 301 mAh g−1 with initial Coulombic efficiency of 93.2%. After 100 cycles, a reversible capacity of 300 mAh g−1 still remains without any obvious decay in voltage. This study sheds light on the comprehensive design and control of oxygen activity in transition-metal-oxide systems for next-generation Li-ion batteries. PMID:27363944

Gas-solid interfacial modification of oxygen activity in layered oxide cathodes for lithium-ion batteries

DOE PAGES

Qiu, Bao; Zhang, Minghao; Wu, Lijun; ...

2016-07-01

Lattice oxygen can play an intriguing role in electrochemical processes, not only maintaining structural stability, but also influencing electron and ion transport properties in high-capacity oxide cathode materials for Li-ion batteries. Here, we report the design of a gas–solid interface reaction to achieve delicate control of oxygen activity through uniformly creating oxygen vacancies without affecting structural integrity of Li-rich layered oxides. Theoretical calculations and experimental characterizations demonstrate that oxygen vacancies provide a favourable ionic diffusion environment in the bulk and significantly suppress gas release from the surface. The target material is achievable in delivering a discharge capacity as high asmore » 301 mAh g –1 with initial Coulombic efficiency of 93.2%. After 100 cycles, a reversible capacity of 300 mAh g –1 still remains without any obvious decay in voltage. Lastly, this study sheds light on the comprehensive design and control of oxygen activity in transition-metal-oxide systems for next-generation Li-ion batteries.« less

Tuning interfacial exchange interactions via electronic reconstruction in transition-metal oxide heterostructures

DOE PAGES

Li, Binzhi; Chopdekar, Rajesh V.; N'Diaye, Alpha T.; ...

2016-10-10

The impact of interfacial electronic reconstruction on the magnetic characteristics of La0.7Sr0.3CoO3 (LSCO)/La0.7Sr0.3MnO3 (LSMO) superlattices was investigated as a function of layer thickness using a combination of soft x-ray magnetic spectroscopy and bulk magnetometry. We found that the magnetic properties of the LSCO layers are impacted by two competing electronic interactions occurring at the LSCO/substrate and LSMO/LSCO interfaces. For thin LSCO layers (< 5 nm), the heterostructures exist in a highly coupled state where the chemically distinct layers behave as a single magnetic compound with magnetically active Co2+ ions. As the LSCO thickness increases, a high coercivity LSCO layer developsmore » which biases a low coercivity layer, which is composed not only of the LSMO layer, but also an interfacial LSCO layer. These results suggest a new route to tune the magnetic properties of transition metal oxide heterostructures through careful control of the interface structure.« less

Multiscale Interfacial Strategy to Engineer Mixed Metal-Oxide Anodes toward Enhanced Cycling Efficiency.

PubMed

Ma, Yue; Tai, Cheuk-Wai; Li, Shaowen; Edström, Kristina; Wei, Bingqing

2018-06-13

Interconnected macro/mesoporous structures of mixed metal oxide (MMO) are developed on nickel foam as freestanding anodes for Li-ion batteries. The sustainable production is realized via a wet chemical etching process with bio-friendly chemicals. By means of divalent iron doping during an in situ recrystallization process, the as-developed MMO anodes exhibit enhanced levels of cycling efficiency. Furthermore, this atomic-scale modification coherently synergizes with the encapsulation layer across a micrometer scale. During this step, we develop a quasi-gel-state tri-copolymer, i.e., F127-resorcinol-melamine, as the N-doped carbon source to regulate the interfacial chemistry of the MMO electrodes. Electrochemical tests of the modified Fe x Ni 1- x O@NC-NiF anode in both half-cell and full-cell configurations unravel the favorable suppression of the irreversible capacity loss and satisfactory cyclability at the high rates. This study highlights a proof-of-concept modification strategy across multiple scales to govern the interfacial chemical process of the electrodes toward better reversibility.

Kinetic-Dominated Charging Mechanism within Representative Aqueous Electrolyte-based Electric Double-Layer Capacitors.

PubMed

Yang, Huachao; Yang, Jinyuan; Bo, Zheng; Chen, Xia; Shuai, Xiaorui; Kong, Jing; Yan, Jianhua; Cen, Kefa

2017-08-03

The chemical nature of electrolytes has been demonstrated to play a pivotal role in the charge storage of electric double-layer capacitors (EDLCs), whereas primary mechanisms are still partially resolved but controversial. In this work, a systematic exploration into EDL structures and kinetics of representative aqueous electrolytes is performed with numerical simulation and experimental research. Unusually, a novel charging mechanism exclusively predominated by kinetics is recognized, going beyond traditional views of manipulating capacitances preferentially via interfacial structural variations. Specifically, strikingly distinctive EDL structures stimulated by diverse ion sizes, valences, and mixtures manifest a virtually identical EDL capacitance, where the dielectric nature of solvents attenuates ionic effects on electrolyte redistributions, in stark contradiction with solvent-free counterpart and traditional Helmholtz theory. Meanwhile, corresponding kinetics evolve conspicuously with ionic species, intimately correlated with ion-solvent interactions. The achieved mechanisms are subsequently illuminated by electrochemical measurements, highlighting the crucial interplay between ions and solvents in regulating EDLC performances.

Heat transfer enhancement in a lithium-ion cell through improved material-level thermal transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vishwakarma, Vivek; Waghela, Chirag; Wei, Zi

2016-09-25

We report that while Li-ion cells offer excellent electrochemical performance for several applications including electric vehicles, they also exhibit poor thermal transport characteristics, resulting in reduced performance, overheating and thermal runaway. Inadequate heat removal from Li-ion cells originates from poor thermal conductivity within the cell. This paper identifies the rate-limiting material-level process that dominates overall thermal conduction in a Li-ion cell. Results indicate that thermal characteristics of a Li-ion cell are largely dominated by heat transfer across the cathode-separator interface rather than heat transfer through the materials themselves. This interfacial thermal resistance contributes around 88% of total thermal resistance inmore » the cell. Measured value of interfacial resistance is close to that obtained from theoretical models that account for weak adhesion and large acoustic mismatch between cathode and separator. Further, to address this problem, an amine-based chemical bridging of the interface is carried out. This is shown to result in in four-times lower interfacial thermal resistance without deterioration in electrochemical performance, thereby increasing effective thermal conductivity by three-fold. This improvement is expected to reduce peak temperature rise during operation by 60%. Finally, by identifying and addressing the material-level root cause of poor thermal transport in Li-ion cells, this work may contribute towards improved thermal performance of Li-ion cells.« less

Resonant Soft X-ray Scattering as a Powerful Probe of Buried Polymer Interfaces

NASA Astrophysics Data System (ADS)

Chen, Wei; Jiang, Zhang; Tirrell, Matthew

Elucidation of polymer interfacial structures provides insights into interfacial molecular mechanisms for coating protection, adhesion, lubrication, friction, wettability, biocompatibility, and even charge transport properties. Resonant Soft X-ray Scattering (RSoXS) offers a unique element, site and valence specific probe to study spatial modulations of molecular orbital degrees of freedom on the nanoscopic length scale. This unique sensitivity is achieved by merging small angle x-ray scattering and x-ray absorption spectroscopy into a single experiment, where the scattering provides information about spatial modulations and the spectroscopy provides sensitivity to the molecular anisotropy. Here we applied RSoXS to polystyrene (PS) films at solid-solid interfaces and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) brushes at solid-liquid interfaces. It is found that the interfacial width of PS thin film is about one order of magnitude large than those observed by traditional scattering techniques. In addition, although the ion-induced changes of PMPC thickness are not apparent in aqueous solutions, their chain conformations like polyzwitterion distribution and correlation varied, dependent on salt types, ionic strengths and ion valences. Consequently, it is evident that RSoXS is a powerful probe of buried polymer interlaces with both spatial and chemical sensitivities. This work was supported by the U.S. Department of Energy, Office of Science, Program in Basic Energy Sciences, Division of Materials Science and Engineering.

Interfacial characteristics and multiferroic properties of ion-doped BiFeO3/NiFe2O4 thin films

NASA Astrophysics Data System (ADS)

Guo, Meiyou; Tan, Guoqiang; Zheng, Yujuan; Liu, Wenlong; Ren, Huijun; Xia, Ao

2017-05-01

Multi-ion doped BiFeO3/NiFe2O4 bilayered thin films were successfully prepared on fluorine-doped SnO2/glass (SnO2:F) substrates by sol-gel method. The crystalline structure, leakage current, interfacial characteristics, and multiferroic properties were investigated in detail. The results of Rietveld refinement showed that the structure of BSrSFMC layer is transformed from rhombohedral to tetragonal structure by the means of ion-doping. The difference of leakage current density of the BSrSFMC/NiFe2O4 (NFO) bilayered films of the -40 V to 40 V and 40 V to -40 V are 0.32 × 10-5 and 1.13 × 10-5 A/cm2, respectively. It was observed that there are obvious interface effects between BSrSFMC and NFO layers, which will cause the accumulation of space charges and the establishment of built-in internal electric field (EI) at the interface. Therefore, different EI directions will affect the dipoles reversal and migration of carriers in the BSrSFMC layer, which will result in different values of transient current with the same applied voltage in the opposite directions. The larger coercive field (Ec ˜ 750 kV/cm) of BSrSFMC/NFO film indicated that there is a tensile stress at the interface between BSrSFMC and NFO layers, making the polarization difficult. These results showed that the above interesting phenomena of the J-V are closely related to the interface effects between the layer of BiFeO3 and NiFe2O4.

Specific effects of Ca2+ ions and molecular structure of β-lactoglobulin interfacial layers that drive macroscopic foam stability† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sm00636a Click here for additional data file.

PubMed Central

Schulze-Zachau, Felix; Nagel, Eva; Engelhardt, Kathrin; Stoyanov, Stefan; Gochev, Georgi; Khristov, Khr.; Mileva, Elena; Exerowa, Dotchi; Miller, Reinhard; Peukert, Wolfgang

2016-01-01

β-Lactoglobulin (BLG) adsorption layers at air–water interfaces were studied in situ with vibrational sum-frequency generation (SFG), tensiometry, surface dilatational rheology and ellipsometry as a function of bulk Ca2+ concentration. The relation between the interfacial molecular structure of adsorbed BLG and the interactions with the supporting electrolyte is additionally addressed on higher length scales along the foam hierarchy – from the ubiquitous air–water interface through thin foam films to macroscopic foam. For concentrations <1 mM, a strong decrease in SFG intensity from O–H stretching bands and a slight increase in layer thickness and surface pressure are observed. A further increase in Ca2+ concentrations above 1 mM causes an apparent change in the polarity of aromatic C–H stretching vibrations from interfacial BLG which we associate to a charge reversal at the interface. Foam film measurements show formation of common black films at Ca2+ concentrations above 1 mM due to considerable decrease of the stabilizing electrostatic disjoining pressure. These observations also correlate with a minimum in macroscopic foam stability. For concentrations >30 mM Ca2+, micrographs of foam films show clear signatures of aggregates which tend to increase the stability of foam films. Here, the interfacial layers have a higher surface dilatational elasticity. In fact, macroscopic foams formed from BLG dilutions with high Ca2+ concentrations where aggregates and interfacial layers with higher elasticity are found, showed the highest stability with much smaller bubble sizes. PMID:27337699

Hydrated interfacial ions and electrons.

PubMed

Abel, Bernd

2013-01-01

Charged particles such as hydrated ions and transient hydrated electrons, the simplest anionic reducing agents in water, and the special hydronium and hydroxide ions at water interfaces play an important role in many fields of science, such as atmospheric chemistry, radiation chemistry, and biology, as well as biochemistry. This article focuses on these species near hydrophobic interfaces of water, such as the air or vacuum interface of water or water protein/membrane interfaces. Ions at interfaces as well as solvated electrons have been reviewed frequently during the past decade. Although all species have been known for some time with seemingly familiar features, recently the picture in all cases became increasingly diffuse rather than clearer. The current account gives a critical state-of-the art overview of what is known and what remains to be understood and investigated about hydrated interfacial ions and electrons.

Electromigration-induced drift in damascene and plasma-etched Al(Cu). II. Mass transport mechanisms in bamboo interconnects

NASA Astrophysics Data System (ADS)

Proost, Joris; Maex, Karen; Delacy, Luc

2000-01-01

We have discussed electromigration (EM)-induced drift in polycrystalline damascene versus reactive ion etched (RIE) Al(Cu) in part I. For polycrystalline Al(Cu), mass transport is well documented to occur through sequential stages : an incubation period (attributed to Cu depletion beyond a critical length) followed by the Al drift stage. In this work, the drift behavior of bamboo RIE and damascene Al(Cu) is analyzed. Using Blech-type test structures, mass transport in RIE lines was shown to proceed both by lattice and interfacial diffusion. The dominating mechanism depends on the Cu distribution in the line, as was evidenced by comparing as-patterned (lattice EM) and RTP-annealed (interface EM) samples. The interfacial EM only occurs at metallic interfaces. In that case, Cu alloying was observed to retard Al interfacial mass transport, giving rise to an incubation time. Although the activation energy for the incubation time was found similar to the one controlling Al lattice drift, for which no incubation time was observed, lattice EM is preferred over interfacial EM because it is insensitive to enhancing geometrical effects upon scaling. When comparing interfacial electromigration in RIE with bamboo damascene Al(Cu), with the incubation time rate controlling for both, the higher EM threshold observed for damascene was shown to be insufficient to compensate for its significantly increased Cu depletion rate, contrary to the case of polycrystalline Al(Cu) interconnects. Two factors were demonstrated to contribute. First, there are more metallic interfaces, intrinsically related to the use of wetting or barrier layers in recessed features. Second, specific to this study, the additional formation of TiAl3 at the trench sidewalls further enhanced the Cu depletion rate, and reduced the rate-controlling incubation time. A separate drift study on RIE via-type test structures indicated that it is very difficult to suppress interfacial mass transport in favor of lattice EM upon TiAl3 formation.

Mixed system of Eudragit s-100 with a designed amphipathic peptide: control of interfacial elasticity by solution composition.

PubMed

Dexter, Annette F; Malcolm, Andrew S; Zeng, Biyun; Kennedy, Debora; Middelberg, Anton P J

2008-04-01

We report an interfacially active system based on an informational peptide surfactant mixed with an oppositely charged polyelectrolyte. The 21-residue cationic peptide, AM1, has previously been shown to respond reversibly to pH and metal ions at fluid interfaces, forming elastic films that can be rapidly switched to collapse foams or emulsions on demand. Here we report the reversible association of AM1 with the methacrylate-based anionic polymer Eudragit S-100. The strength of the association, in bulk aqueous solution, is modulated by added metal ions and by ionic strength. Addition of zinc ions to the peptide-polymer system promotes complex formation and phase separation, while addition of a chelating agent reverses the association. The addition of salt weakens peptide-polymer interactions in the presence or absence of zinc. At the air-water interface, Eudragit S-100 forms an elastic mixed film with AM1 in the absence of metal, under conditions where the peptide alone does not show interfacial elasticity. When zinc is present, the elasticity of the mixed film is increased, but the rate of interfacial adsorption slows due to formation of peptide-polymer complexes in bulk solution. An understanding of these interactions can be used to identify favorable foam-forming conditions in the mixed system.

Effect of Co doping on the structural and dielectric properties of ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ram, Mast, E-mail: Mastram1999@yahoo.com; Bala, Kanchan; Sharma, Hakikat

This paper reports on the synthesis of Co doped Zn{sub 1-x}Co{sub x}O (x= 0.0, 0.01, 0.02, 0.03 and 0.05) nanoparticles by solution combustion method using urea as a fuel. The Structural and dielectric properties of the samples were studied. Crystallite sizes were obtained from X-ray diffraction (XRD) patterns whose values decreased with increase in Co concentration. The XRD study reveals that Co{sup 2+} ions substitute the Zn{sup 2+} ion without changing the wurtzite structure of pristine ZnO up to Co concentrations of 5%. The dielectric constants, dielectric loss (tanδ) and ac conductivity (σ{sub ac}) were studied as the function ofmore » frequency and composition, which have been explained by Maxwell-Wagner type interfacial polarization and discussed Koops phenomenological theory.« less

Molecular Dynamics Studies of Structure and Functions of Water-Membrane Interfaces

NASA Technical Reports Server (NTRS)

Pohorille, Andrew; Wilson, Michael A.; DeVincenzi, Donald L. (Technical Monitor)

2001-01-01

A large number of essential cellular processes occur at the interfaces between water and membranes. The selectivity and dynamics of these processes are largely determined by the structural and electrical properties of the water-membrane interface. We investigate these properties by the molecular dynamics method. Over the time scales of the simulations, the membrane undergoes fluctuations described by the capillary wave model. These fluctuations produce occasional thinning defects in the membrane which provide effective pathways for passive transport of ions and small molecules across the membrane. Ions moving through the membrane markedly disrupt its structure and allow for significant water penetration into the membrane interior. Selectivity of transport, with respect to ionic charge, is determined by the interfacial electrostatic potential. Many small molecules. of potential significance in catalysis, bioenergetics and pharmacology, are shown to bind to the interface. The energetics and dynamics of this process will be discussed.

Fischer Indole Synthesis in the Gas Phase, the Solution Phase, and at the Electrospray Droplet Interface.

PubMed

Bain, Ryan M; Ayrton, Stephen T; Cooks, R Graham

2017-07-01

Previous reports have shown that reactions occurring in the microdroplets formed during electrospray ionization can, under the right conditions, exhibit significantly greater rates than the corresponding bulk solution-phase reactions. The observed acceleration under electrospray ionization could result from a solution-phase, a gas-phase, or an interfacial reaction. This study shows that a gas-phase ion/molecule (or ion/ion) reaction is not responsible for the observed rate enhancement in the particular case of the Fischer indole synthesis. The results show that the accelerated reaction proceeds in the microdroplets, and evidence is provided that an interfacial process is involved. Graphical Abstract .

Interfacial crystalline structures in injection over-molded polypropylene and bond strength.

PubMed

Yan, Bowen; Wu, Hong; Jiang, Genjie; Guo, Shaoyun; Huang, Jian

2010-11-01

This paper describes interfacial crystalline structures found in injection overmolded polypropylene components and the relationship of these structures to bond strength between the components. The combined effects of the development of hierarchical gradient structures and the particular thermomechanical environment near the interface on the interfacial crystalline structures were investigated in detail by PLM, SEM, DSC, WAXD, and infrared dichroism spectroscopy. The experimental results showed that during molding there was competitive formation of interfacial crystalline structures consisted of "shish-kebab" layer (SKL) and a transcrystalline layers (TCL). Variation in shear stress (controlled by injection pressure and injection speed) plays an important role in the formation of the SKL. The formation of TCL is influenced by the thermal environment, namely melt temperature and mold temperature. Increasing within certain limits, interfacial temperature and the thermal gradient near the interface promotes β-iPP growth. The relationship between interfacial crystalline structures and interfacial bond strength was established by lap shear measurement. The interfacial bond strength is improved by enhancing the formation of TCL, but reduced if SKL predominates.

Nanoscale interfacial mixing of Au/Bi layers using MeV ion beams

NASA Astrophysics Data System (ADS)

Prusty, Sudakshina; Siva, V.; Ojha, S.; Kabiraj, D.; Sahoo, P. K.

2017-05-01

We have studied nanoscale mixing of thermally deposited double bilayer films of Au/Bi after irradiating them by 1.5 MeV Au2+ ions. Post irradiation effects on the morphology and elemental identification in these films are studied by Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS). Glancing angle X-ray diffraction (GAXRD) of the samples indicate marginal changes in the irradiated samples due to combined effect of nuclear and electronic energy loss. The interfacial mixing is studied by Rutherford backscattering (RBS).

Stress evolution in elastic-plastic electrodes during electrochemical processes: A numerical method and its applications

NASA Astrophysics Data System (ADS)

Wen, Jici; Wei, Yujie; Cheng, Yang-Tse

2018-07-01

Monitoring in real time the stress state in high capacity electrodes during charge-discharge processes is pivotal to the performance assessment and structural optimization of advanced batteries. The wafer curvature measurement technique broadly employed in thin-film industry, together with stress analysis using the Stoney equation, has been successfully adopted to measure in situ the stress in thin film electrodes. How large plastic deformation or interfacial delamination during electrochemical cycles in such electrodes affects the applicability of Stoney equation remains unclear. Here we develop a robust electrochemical-mechanical coupled numerical procedure to investigate the influence of large plastic deformation and interfacial failure on the measured stress in thin film electrodes. We identify how the constitutive behavior of electrode materials and film-substrate interfacial properties affect the measured stress-capacity curves of electrodes, and hence establish the relationship of electrode material parameters with the characteristics of stress-capacity curves. Using Li-ions batteries as examples, we show that plastic deformation and interfacial delamination account for the asymmetric stress-capacity loops seen in in situ stress measurements. The methods used here, along with the finite-element code in the supplementary material, may be used to model the electrode behavior as a function of the state of charge.

Electrostatic Self-Assembly Enabling Integrated Bulk and Interfacial Sodium Storage in 3D Titania-Graphene Hybrid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Gui-Liang; Xiao, Lisong; Sheng, Tian

Room temperature sodium-ion batteries have attracted increased attention for energy storage due to the natural abundance of sodium. However, it remains a huge challenge to develop versatile electrode materials with favorable properties, which requires smart structure design and good mechanistic understanding. Herein, we reported a general and scalable approach to synthesize 3D titania-graphene hybrid via electrostatic-interaction-induced self-assembly. Synchrotron X-ray probe, transmission electron microscopy and computational modeling revealed that the strong interaction between Titania and graphene through comparably strong van-der-Waals forces not only facilitates bulk Na+ intercalation but also enhances the interfacial sodium storage. As a result, the titania-graphene hybrid exhibitsmore » exceptional long-term cycle stability up to 5000 cycles, and ultrahigh rate capability up to 20 C for sodium storage. Furthermore, density function theory calculation indicated that the interfacial Li+, K+, Mg2+ and Al3+ storage can be enhanced as well. The proposed general strategy opens up new avenues to create versatile materials for advanced battery systems.« less

Electrostatic Self-Assembly Enabling Integrated Bulk and Interfacial Sodium Storage in 3D Titania-Graphene Hybrid.

PubMed

Xu, Gui-Liang; Xiao, Lisong; Sheng, Tian; Liu, Jianzhao; Hu, Yi-Xin; Ma, Tianyuan; Amine, Rachid; Xie, Yingying; Zhang, Xiaoyi; Liu, Yuzi; Ren, Yang; Sun, Cheng-Jun; Heald, Steve M; Kovacevic, Jasmina; Sehlleier, Yee Hwa; Schulz, Christof; Mattis, Wenjuan Liu; Sun, Shi-Gang; Wiggers, Hartmut; Chen, Zonghai; Amine, Khalil

2018-01-10

Room-temperature sodium-ion batteries have attracted increased attention for energy storage due to the natural abundance of sodium. However, it remains a huge challenge to develop versatile electrode materials with favorable properties, which requires smart structure design and good mechanistic understanding. Herein, we reported a general and scalable approach to synthesize three-dimensional (3D) titania-graphene hybrid via electrostatic-interaction-induced self-assembly. Synchrotron X-ray probe, transmission electron microscopy, and computational modeling revealed that the strong interaction between titania and graphene through comparably strong van der Waals forces not only facilitates bulk Na + intercalation but also enhances the interfacial sodium storage. As a result, the titania-graphene hybrid exhibits exceptional long-term cycle stability up to 5000 cycles, and ultrahigh rate capability up to 20 C for sodium storage. Furthermore, density function theory calculation indicated that the interfacial Li + , K + , Mg 2+, and Al 3+ storage can be enhanced as well. The proposed general strategy opens up new avenues to create versatile materials for advanced battery systems.

Molecular dynamics simulations of n-hexane at 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lisal, Martin; Department of Physics, Faculty of Science, J. E. Purkinje University, 400 96 Usti n. Lab.; Izak, Pavel

Molecular dynamics simulations of n-hexane adsorbed onto the interface of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][Tf{sub 2}N]) are performed at three n-hexane surface densities, ranged from 0.7 to 2.3 {mu}mol/m{sup 2} at 300 K. For [bmim][Tf{sub 2}N] room-temperature ionic liquid, we use a non-polarizable all-atom force field with the partial atomic charges based on ab initio calculations for the isolated ion pair. The net charges of the ions are {+-}0.89e, which mimics the anion to cation charge transfer and polarization effects. The OPLS-AA force field is employed for modeling of n-hexane. The surface tension is computed using the mechanical route and itsmore » value decreases with increase of the n-hexane surface density. The [bmim][Tf{sub 2}N]/n-hexane interface is analyzed using the intrinsic method, and the structural and dynamic properties of the interfacial, sub-interfacial, and central layers are computed. We determine the surface roughness, global and intrinsic density profiles, and orientation ordering of the molecules to describe the structure of the interface. We further compute the survival probability, normal and lateral self-diffusion coefficients, and re-orientation correlation functions to elucidate the effects of n-hexane on dynamics of the cations and anions in the layers.« less

Molecular dynamics simulations of n-hexane at 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide interface.

PubMed

Lísal, Martin; Izák, Pavel

2013-07-07

Molecular dynamics simulations of n-hexane adsorbed onto the interface of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][Tf2N]) are performed at three n-hexane surface densities, ranged from 0.7 to 2.3 μmol/m(2) at 300 K. For [bmim][Tf2N] room-temperature ionic liquid, we use a non-polarizable all-atom force field with the partial atomic charges based on ab initio calculations for the isolated ion pair. The net charges of the ions are ±0.89e, which mimics the anion to cation charge transfer and polarization effects. The OPLS-AA force field is employed for modeling of n-hexane. The surface tension is computed using the mechanical route and its value decreases with increase of the n-hexane surface density. The [bmim][Tf2N]/n-hexane interface is analyzed using the intrinsic method, and the structural and dynamic properties of the interfacial, sub-interfacial, and central layers are computed. We determine the surface roughness, global and intrinsic density profiles, and orientation ordering of the molecules to describe the structure of the interface. We further compute the survival probability, normal and lateral self-diffusion coefficients, and re-orientation correlation functions to elucidate the effects of n-hexane on dynamics of the cations and anions in the layers.

On the mechanisms of cation injection in conducting bridge memories: The case of HfO{sub 2} in contact with noble metal anodes (Au, Cu, Ag)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saadi, M.; CNRS, LTM, F-38000 Grenoble; El Manar University, LMOP, 2092 Tunis

Resistance switching is studied in HfO{sub 2} as a function of the anode metal (Au, Cu, and Ag) in view of its application to resistive memories (resistive random access memories, RRAM). Current-voltage (I-V) and current-time (I-t) characteristics are presented. For Au anodes, resistance transition is controlled by oxygen vacancies (oxygen-based resistive random access memory, OxRRAM). For Ag anodes, resistance switching is governed by cation injection (Conducting Bridge random access memory, CBRAM). Cu anodes lead to an intermediate case. I-t experiments are shown to be a valuable tool to distinguish between OxRRAM and CBRAM behaviors. A model is proposed to explainmore » the high-to-low resistance transition in CBRAMs. The model is based on the theory of low-temperature oxidation of metals (Cabrera-Mott theory). Upon electron injection, oxygen vacancies and oxygen ions are generated in the oxide. Oxygen ions are drifted to the anode, and an interfacial oxide is formed at the HfO{sub 2}/anode interface. If oxygen ion mobility is low in the interfacial oxide, a negative space charge builds-up at the HfO{sub 2}/oxide interface. This negative space charge is the source of a strong electric field across the interfacial oxide thickness, which pulls out cations from the anode (CBRAM case). Inversely, if oxygen ions migration through the interfacial oxide is important (or if the anode does not oxidize such as Au), bulk oxygen vacancies govern resistance transition (OxRRAM case).« less

Interfacial Ferromagnetism and Exchange Bias in CaRuO3/CaMnO3 Superlattices

NASA Astrophysics Data System (ADS)

He, C.; Grutter, A. J.; Gu, M.; Browning, N. D.; Takamura, Y.; Kirby, B. J.; Borchers, J. A.; Kim, J. W.; Fitzsimmons, M. R.; Zhai, X.; Mehta, V. V.; Wong, F. J.; Suzuki, Y.

2012-11-01

We have found ferromagnetism in epitaxially grown superlattices of CaRuO3/CaMnO3 that arises in one unit cell at the interface. Scanning transmission electron microscopy and electron energy loss spectroscopy indicate that the difference in magnitude of the Mn valence states between the center of the CaMnO3 layer and the interface region is consistent with double exchange interaction among the Mn ions at the interface. Polarized neutron reflectivity and the CaMnO3 thickness dependence of the exchange bias field together indicate that the interfacial ferromagnetism is only limited to one unit cell of CaMnO3 at each interface. The interfacial moment alternates between the 1μB/interface Mn ion for even CaMnO3 layers and the 0.5μB/interface Mn ion for odd CaMnO3 layers. This modulation, combined with the exchange bias, suggests the presence of a modulating interlayer coupling between neighboring ferromagnetic interfaces via the antiferromagnetic CaMnO3 layers.

Development of large-surface Nafion-metal composite actuator and its electrochemical characterization

NASA Astrophysics Data System (ADS)

Noh, Taegeun; Tak, Yong Suk; Nam, Jaedo; Jeon, Jaewook; Kim, Hunmo; Choi, Hyoukryeol; Bae, Sang Sik

2001-07-01

Behaviors of nafion-based actuators are significantly affected by interfacial area between electrode and polymer electrolyte. Replication method was utilized to manufacture a large surface-area composite actuator. Etched aluminum foil was used as a template for replication using liquid nafion solution. Measurement of double layer charging and scanning electron microscopy indicated that interfacial area was greatly increased by replication method. Higher surface area induced a better bending performance of ionic polymer metal composite (IPMC). In parallel, the effect of cations on IPMC was interpreted with constant current experiment, linear sweep voltammetry and electrochemical impedance spectroscopy. For univalent cations, ion size is the most influencing parameter on ionic mobility inside membrane. However, ion-ion interaction affects an ionic mobility for divalent cations.

Fundamental aspects of electric double layer force-distance measurements at liquid-solid interfaces using atomic force microscopy

PubMed Central

Black, Jennifer M.; Zhu, Mengyang; Zhang, Pengfei; Unocic, Raymond R.; Guo, Daqiang; Okatan, M. Baris; Dai, Sheng; Cummings, Peter T.; Kalinin, Sergei V.; Feng, Guang; Balke, Nina

2016-01-01

Atomic force microscopy (AFM) force-distance measurements are used to investigate the layered ion structure of Ionic Liquids (ILs) at the mica surface. The effects of various tip properties on the measured force profiles are examined and reveal that the measured ion position is independent of tip properties, while the tip radius affects the forces required to break through the ion layers as well as the adhesion force. Force data is collected for different ILs and directly compared with interfacial ion density profiles predicted by molecular dynamics. Through this comparison it is concluded that AFM force measurements are sensitive to the position of the ion with the larger volume and mass, suggesting that ion selectivity in force-distance measurements are related to excluded volume effects and not to electrostatic or chemical interactions between ions and AFM tip. The comparison also revealed that at distances greater than 1 nm the system maintains overall electroneutrality between the AFM tip and sample, while at smaller distances other forces (e.g., van der waals interactions) dominate and electroneutrality is no longer maintained. PMID:27587276

Hydration structure of the barite (001)–water interface: Comparison of x-ray reflectivity with molecular dynamics simulations

DOE PAGES

Bracco, Jacquelyn N.; Lee, Sang Soo; Stubbs, Joanne E.; ...

2017-05-11

The three-dimensional structure of the barite (001)-water interface was studied using in situ specular and non-specular X-ray reflectivity (XR). Displacements of the barium and sulfate ions in the surface of a barite crystal and the interfacial water structure were defined in the analyses. The largest relaxations (0.13 Å lateral and 0.08 Å vertical) were observed for the barium and sulfate ions in the topmost unit cell layer, which diminished rapidly with depth. The best fit structure identified four distinct adsorbed species, which in comparison with molecular dynamics (MD) simulations, reveals that they are associated with positions of adsorbed water, eachmore » of which coordinates one or two surface ions (either barium, sulfate, or both). These water molecules also adsorb in positions consistent with those of bariums and sulfates in the bulk crystal lattice. These results demonstrate the importance of combining high resolution XR with MD simulations to fully describe the atomic structure of the hydrated mineral surface. As a result, the agreement between the results indicates both the uniqueness of the structural model obtained from the XR analysis and the accuracy of the force field used in the simulations.« less

Hydration structure of the barite (001)–water interface: Comparison of x-ray reflectivity with molecular dynamics simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bracco, Jacquelyn N.; Lee, Sang Soo; Stubbs, Joanne E.

The three-dimensional structure of the barite (001)-water interface was studied using in situ specular and non-specular X-ray reflectivity (XR). Displacements of the barium and sulfate ions in the surface of a barite crystal and the interfacial water structure were defined in the analyses. The largest relaxations (0.13 Å lateral and 0.08 Å vertical) were observed for the barium and sulfate ions in the topmost unit cell layer, which diminished rapidly with depth. The best fit structure identified four distinct adsorbed species, which in comparison with molecular dynamics (MD) simulations, reveals that they are associated with positions of adsorbed water, eachmore » of which coordinates one or two surface ions (either barium, sulfate, or both). These water molecules also adsorb in positions consistent with those of bariums and sulfates in the bulk crystal lattice. These results demonstrate the importance of combining high resolution XR with MD simulations to fully describe the atomic structure of the hydrated mineral surface. As a result, the agreement between the results indicates both the uniqueness of the structural model obtained from the XR analysis and the accuracy of the force field used in the simulations.« less

N-Allyl- N, N-Bis(trimethylsilyl)amine as a Novel Electrolyte Additive To Enhance the Interfacial Stability of a Ni-Rich Electrode for Lithium-Ion Batteries.

PubMed

Zheng, Qinfeng; Xing, Lidan; Yang, Xuerui; Li, Xiangfeng; Ye, Changchun; Wang, Kang; Huang, Qiming; Li, Weishan

2018-05-16

Enhancing the electrode/electrolyte interface stability of high-capacity LiNi 0.8 Co 0.15 Al 0.05 O 2 (LNCA) cathode material is urgently required for its application in next-generation lithium-ion battery. Herein, we demonstrate that enhanced interfacial stability of LNCA can be achieved by simply introducing 2 wt % N-allyl- N, N-bis(trimethylsilyl)amine (NNB) electrolyte additive. Electrolyte oxidation reactions and electrode structural destruction are greatly suppressed in the electrolyte with NNB additive, leading to improved cyclic stability of LNCA from 72.8 to 86.2% after 300 cycles. The mechanism of NNB on improving the cyclic stability of LNCA has been verified to its excellent solid electrolyte interface (SEI) film-forming capability. Moreover, the X-ray diffraction and X-ray photoelectron spectroscopy results indicate that the NNB-derived Si-containing SEI film restrains the Li/Ni disorder of LNCA during cycling, which further improves the cyclic stability of Ni-rich LNCA. Importantly, the charging/discharging test reveals that the NNB additive effectively improves the cyclic stability of the LNCA/graphite full cell.

A Top-Down Strategy toward SnSb In-Plane Nanoconfined 3D N-Doped Porous Graphene Composite Microspheres for High Performance Na-Ion Battery Anode.

PubMed

Qin, Jian; Wang, Tianshuai; Liu, Dongye; Liu, Enzuo; Zhao, Naiqin; Shi, Chunsheng; He, Fang; Ma, Liying; He, Chunnian

2018-03-01

Engineering of 3D graphene/metal composites with ultrasmall sized metal and robust metal-graphene interfacial interaction for energy storage application is still a challenge and rarely reported. In this work, a facile top-down strategy is developed for the preparation of SnSb-in-plane nanoconfined 3D N-doped porous graphene networks for sodium ion battery anodes, which are composed of several tens of interconnected empty N-graphene boxes in-plane firmly embedded with ultrasmall SnSb nanocrystals. The all-around encapsulation (plane-to-plane contact) architecture that provides a large interface between N-graphene and SnSb nanocrystal not only effectively enhances the electron conductivity and structural integrity of the overall electrode, but also offers excess interfacial sodium storage, thus leading to much enhanced high-rate sodium storage capacity and stability, which has been proven by both experimental results and first-principles simulations. Moreover, this top-down strategy can enable new paths to the low-cost and high-yield synthesis of 3D graphene/metal composites for applications in energy-related fields and beyond. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mastering the interface for advanced all-solid-state lithium rechargeable batteries

PubMed Central

Li, Yutao; Zhou, Weidong; Chen, Xi; Lü, Xujie; Cui, Zhiming; Xin, Sen; Xue, Leigang; Jia, Quanxi; Goodenough, John B.

2016-01-01

A solid electrolyte with a high Li-ion conductivity and a small interfacial resistance against a Li metal anode is a key component in all-solid-state Li metal batteries, but there is no ceramic oxide electrolyte available for this application except the thin-film Li-P oxynitride electrolyte; ceramic electrolytes are either easily reduced by Li metal or penetrated by Li dendrites in a short time. Here, we introduce a solid electrolyte LiZr2(PO4)3 with rhombohedral structure at room temperature that has a bulk Li-ion conductivity σLi = 2 × 10−4 S⋅cm−1 at 25 °C, a high electrochemical stability up to 5.5 V versus Li+/Li, and a small interfacial resistance for Li+ transfer. It reacts with a metallic lithium anode to form a Li+-conducting passivation layer (solid-electrolyte interphase) containing Li3P and Li8ZrO6 that is wet by the lithium anode and also wets the LiZr2(PO4)3 electrolyte. An all-solid-state Li/LiFePO4 cell with a polymer catholyte shows good cyclability and a long cycle life. PMID:27821751

Interfacial solvation thermodynamics

NASA Astrophysics Data System (ADS)

Ben-Amotz, Dor

2016-10-01

Previous studies have reached conflicting conclusions regarding the interplay of cavity formation, polarizability, desolvation, and surface capillary waves in driving the interfacial adsorptions of ions and molecules at air-water interfaces. Here we revisit these questions by combining exact potential distribution results with linear response theory and other physically motivated approximations. The results highlight both exact and approximate compensation relations pertaining to direct (solute-solvent) and indirect (solvent-solvent) contributions to adsorption thermodynamics, of relevance to solvation at air-water interfaces, as well as a broader class of processes linked to the mean force potential between ions, molecules, nanoparticles, proteins, and biological assemblies.

Rational composition control of mixed-lanthanide metal-organic frameworks by an interfacial reaction with metal ion-doped polymer substrates

NASA Astrophysics Data System (ADS)

Tsuruoka, Takaaki; Miyanaga, Ayumi; Ohhashi, Takashi; Hata, Manami; Takashima, Yohei; Akamatsu, Kensuke

2017-09-01

A simple composition control route to mixed-lanthanide metal-organic frameworks (MOFs) was developed based on an interfacial reaction with mixed-lanthanide metal ion-doped polymer substrates. By controlling the composition of lanthanide ion (Eu3+ and Tb3+) dopants in polymer substrates to be used as metal ion precursors and scaffolding for the formation of MOFs, [EuxTb2-x(bdc)3(H2O)4]n crystals with a tunable metal composition could be routinely prepared on polymer substrates. Inductively coupled plasma (ICP) measurements revealed that the composition of the obtained frameworks was almost the same as that of the initial polymer substrates. In addition, the resulting [EuxTb2-x(bdc)3(H2O)4]n crystals showed strong phosphorescence because of Eu3+ transitions, indicating that the energy transfer from Tb3+ to Eu3+ ions in the frameworks could be achieved with high efficiency.

Molecular dynamics simulations of pyrrolidinium and imidazolium ionic liquids at graphene interfaces.

PubMed

Begić, Srđan; Jónsson, Erlendur; Chen, Fangfang; Forsyth, Maria

2017-11-15

Understanding the electrode-electrolyte interface is essential in the battery research as the ion transport and ion structures at the interface most likely affect the performance of a battery. Here we investigate interfacial structures of three ionic liquids: 1-ethyl-3-methylimidazolium dicyanamide ([C 2 mim][dca]), 1-butyl-3-methylimidazolium dicyanamide ([C 4 mim][dca]) and N-butyl-N-methylpyrrolidinium dicyanamide ([C 4 myr][dca]) at a charged and uncharged graphene interface using molecular dynamics simulations. We find that these ionic liquids (ILs) behave differently both in the bulk phase and near a graphene interface and we find that this difference is apparent in all types of analyses performed here. First, a partial density analysis in the direction perpendicular to the surface of the electrodes, which, in the cases near a negatively charged graphene, reveals that the pyrrolidinium system is generally more layered than the imidazolium systems. Second, a 2D topographic structure analysis of the IL species in the inner layer near a negatively charged graphene surface, which reveals that the pyrrolidinium system exhibits a quasi-hexagonal surface configuration of the cations, while the imidazolium systems show linearly arranged groups of cations. Third, a 3D orientation-preference analysis of cation rings near the negative graphene electrode, which shows that the pyrrolidinium rings prefer to lie parallel to the electrode surface while the imidazolium rings prefer to stand on the electrode surface at high tilt angles. Extending the imidazolium alkyl chain was found to reduce the number of imidazoliums that can link up into linearly arranged groups in the inner layer 2D structures. Our results support earlier experimental findings and indicate that the interfacial nanostructures may have a significant influence on the electrochemical performance of IL-based batteries.

Unified molecular picture of the surfaces of aqueous acid, base, and salt solutions.

PubMed

Mucha, Martin; Frigato, Tomaso; Levering, Lori M; Allen, Heather C; Tobias, Douglas J; Dang, Liem X; Jungwirth, Pavel

2005-04-28

The molecular structure of the interfacial regions of aqueous electrolytes is poorly understood, despite its crucial importance in many biological, technological, and atmospheric processes. A long-term controversy pertains between the standard picture of an ion-free surface layer and the strongly ion specific behavior indicating in many cases significant propensities of simple inorganic ions for the interface. Here, we present a unified and consistent view of the structure of the air/solution interface of aqueous electrolytes containing monovalent inorganic ions. Molecular dynamics calculations show that in salt solutions and bases the positively charged ions, such as alkali cations, are repelled from the interface, whereas the anions, such as halides or hydroxide, exhibit a varying surface propensity, correlated primarily with the ion polarizability and size. The behavior of acids is different due to a significant propensity of hydronium cations for the air/solution interface. Therefore, both cations and anions exhibit enhanced concentrations at the surface and, consequently, these acids (unlike bases and salts) reduce the surface tension of water. The results of the simulations are supported by surface selective nonlinear vibrational spectroscopy, which reveals among other things that the hydronium cations are present at the air/solution interface. The ion specific propensities for the air/solution interface have important implications for a whole range of heterogeneous physical and chemical processes, including atmospheric chemistry of aerosols, corrosion processes, and bubble coalescence.

Migration of interfacial oxygen ions modulated resistive switching in oxide-based memory devices

NASA Astrophysics Data System (ADS)

Chen, C.; Gao, S.; Zeng, F.; Tang, G. S.; Li, S. Z.; Song, C.; Fu, H. D.; Pan, F.

2013-07-01

Oxides-based resistive switching memory induced by oxygen ions migration is attractive for future nonvolatile memories. Numerous works had focused their attentions on the sandwiched oxide materials for depressing the characteristic variations, but the comprehensive studies of the dependence of electrodes on the migration behavior of oxygen ions are overshadowed. Here, we investigated the interaction of various metals (Ni, Co, Al, Ti, Zr, and Hf) with oxygen atoms at the metal/Ta2O5 interface under electric stress and explored the effect of top electrode on the characteristic variations of Ta2O5-based memory device. It is demonstrated that chemically inert electrodes (Ni and Co) lead to the scattering switching characteristics and destructive gas bubbles, while the highly chemically active metals (Hf and Zr) formed a thick and dense interfacial intermediate oxide layer at the metal/Ta2O5 interface, which also degraded the resistive switching behavior. The relatively chemically active metals (Al and Ti) can absorb oxygen ions from the Ta2O5 film and avoid forming the problematic interfacial layer, which is benefit to the formation of oxygen vacancies composed conduction filaments in Ta2O5 film thus exhibit the minimum variations of switching characteristics. The clarification of oxygen ions migration behavior at the interface can lead further optimization of resistive switching performance in Ta2O5-based memory device and guide the rule of electrode selection for other oxide-based resistive switching memories.

Configuration-specific electronic structure of strongly interacting interfaces: TiOPc on Cu(110)

NASA Astrophysics Data System (ADS)

Maughan, Bret; Zahl, Percy; Sutter, Peter; Monti, Oliver L. A.

2017-12-01

We use low-temperature scanning tunneling microscopy in combination with angle-resolved ultraviolet and two-photon photoemission spectroscopy to investigate the interfacial electronic structure of titanyl phthalocyanine (TiOPc) on Cu(110). We show that the presence of two unique molecular adsorption configurations is crucial for a molecular-level analysis of the hybridized interfacial electronic structure. Specifically, thermally induced self-assembly exposes marked adsorbate-configuration-specific contributions to the interfacial electronic structure. The results of this work demonstrate an avenue towards understanding and controlling interfacial electronic structure in chemisorbed films even for the case of complex film structure.

Requirement of lid2 for interfacial activation of a family I.3 lipase with unique two lid structures.

PubMed

Cheng, Maria; Angkawidjaja, Clement; Koga, Yuichi; Kanaya, Shigenori

2012-10-01

A family I.3 lipase from Pseudomonas sp. MIS38 (PML) is characterized by the presence of two lids (lid1 and lid2) that greatly change conformation upon substrate binding. While lid1 represents the commonly known lid in lipases, lid2 is unique to PML and other family I.3 lipases. To clarify the role of lid2 in PML, a lid2 deletion mutant (ΔL2-PML) was constructed by deleting residues 35-64 of PML. ΔL2-PML requires calcium ions for both lipase and esterase activities as does PML, suggesting that it exhibits activity only when lid1 is fully open and anchored by the catalytically essential calcium ion, as does PML. However, when the enzymatic activity was determined using triacetin, the activity of PML exponentially increased as the substrate concentration reached and increased beyond the critical micellar concentration, while that of ΔL2-PML did not. These results indicate that PML undergoes interfacial activation, while ΔL2-PML does not. The activities of ΔL2-PML for long-chain triglycerides significantly decreased while its activity for fatty acid ethyl esters increased, compared with those of PML. Comparison of the tertiary models of ΔL2-PML in a closed and open conformation, which are optimized by molecular dynamics simulation, with the crystal structures of PML suggests that the hydrophobic surface area provided by lid1 and lid2 in an open conformation is considerably decreased by the deletion of lid2. We propose that the hydrophobic surface area provided by these lids is necessary to hold the micellar substrates firmly to the active site and therefore lid2 is required for interfacial activation of PML. © 2012 The Authors Journal compilation © 2012 FEBS.

Interfacial strain effects on lithium diffusion pathways in the spinel solid electrolyte Li-doped MgAl2O4

NASA Astrophysics Data System (ADS)

O'Rourke, Conn; Morgan, Benjamin J.

2018-04-01

The (Li,Al)-codoped magnesium spinel (LixMg1 -2 xAl2 +xO4 ) is a solid lithium-ion electrolyte with potential use in all-solid-state lithium-ion batteries. The spinel structure means that interfaces with spinel electrodes, such as LiyMn2O4 and Li4 +3 zTi5O12 , may be lattice matched, with potentially low interfacial resistances. Small lattice parameter differences across a lattice-matched interface are unavoidable, causing residual epitaxial strain. This strain potentially modifies lithium diffusion near the electrolyte-electrode interface, contributing to interfacial resistance. Here, we report a density functional theory study of strain effects on lithium diffusion pathways for (Li,Al)-codoped magnesium spinel, for xLi=0.25 and xLi=0.5 . We have calculated diffusion profiles for the unstrained materials, and for isotropic and biaxial tensile strains of up to 6 % , corresponding to {100 } epitaxial interfaces with LiyMn2O4 and Li4 +3 zTi5O12 . We find that isotropic tensile strain reduces lithium diffusion barriers by as much as 0.32 eV , with typical barriers reduced by ˜0.1 eV. This effect is associated with increased volumes of transitional octahedral sites, and broadly follows qualitative changes in local electrostatic potentials. For biaxial (epitaxial) strain, which more closely approximates strain at a lattice-matched electrolyte-electrode interface, changes in octahedral site volumes and in lithium diffusion barriers are much smaller than under isotropic strain. Typical barriers are reduced by only ˜0.05 eV. Individual effects, however, depend on the pathway considered and the relative strain orientation. These results predict that isotropic strain strongly affects ionic conductivities in (Li,Al)-codoped magnesium spinel electrolytes, and that tensile strain is a potential route to enhanced lithium transport. For a lattice-matched interface with candidate spinel-structured electrodes, however, epitaxial strain has a small, but complex, effect on lithium diffusion barriers.

Wear and interfacial transport of material

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1975-01-01

Bonding across the interface for two solids in contact and the subsequent transfer of material from one surface to another is a direct result of the interfacial bonds being stronger than the cohesive bonds in either of the two solids. Surface tools such as LEED, Auger emission spectroscopy, field ion microscopy, and the atom probe are used to examine adhesive contacts and to determine the direction, nature, quantity of material transfer and properties of the solids which effect transfer and wear. The electronic nature, cohesive binding energies, surface structure, lattice disregistry and distribution of species in surface layers are all found to effect adhesion and transfer or transport for clean surfaces in solid state contact. The influence of adsorbed and reacted surface films from fractions of a monolayer to multilayer reactive films are considered. It is shown that even fractions of a monolayer of surface active species such as oxygen and sulfur can markedly inhibit adhesion and transport.

Metal segregation in hierarchically structured cathode materials for high-energy lithium batteries

DOE PAGES

Lin, Feng; Xin, Huolin L.; Nordlund, Dennis; ...

2016-01-11

Controlling surface and interfacial properties of battery materials is key to improving performance in rechargeable Li-ion devices. Surface reconstruction from a layered to a rock salt structure in metal oxide cathode materials is commonly observed and results in poor high-voltage cycling performance, impeding attempts to improve energy density. Hierarchically structured LiNi 0.4Mn 0.4Co 0.2O 2 (NMC-442) spherical powders, made by spray pyrolysis, exhibit local elemental distribution gradients that deviate from the global NMC-442 composition; specifically, they are Ni-rich and Mn-poor at particle surfaces. These materials demonstrate improved Coulombic efficiencies, discharge capacities, and high-voltage capacity retention in lithium half-cell configurations. Themore » subject powders show superior resistance against surface reconstruction due to the tailored surface chemistry, compared to conventional NMC-442 materials. This paves the way towards the development of a new generation of robust and stable high-energy NMC cathodes for Li-ion batteries.« less

Unveiling structural, chemical and magnetic interfacial peculiarities in ε-Fe2O3/GaN (0001) epitaxial films.

PubMed

Ukleev, Victor; Suturin, Sergey; Nakajima, Taro; Arima, Taka-Hisa; Saerbeck, Thomas; Hanashima, Takayasu; Sitnikova, Alla; Kirilenko, Demid; Yakovlev, Nikolai; Sokolov, Nikolai

2018-06-07

The metastable ε-Fe 2 O 3 is known to be the most intriguing ferrimagnetic and multiferroic iron oxide phase exhibiting a bunch of exciting physical properties both below and above room temperature. The present paper unveils the structural and magnetic peculiarities of a few nm thick interface layer discovered in these films by a number of techniques. The polarized neutron reflectometry data suggests that the interface layer resembles GaFeO 3 in composition and density and is magnetically softer than the rest of the ε-Fe 2 O 3 film. While the in-depth density variation is in agreement with the transmission electron microscopy measurements, the layer-resolved magnetization profiles are qualitatively consistent with the unusual wasp-waist magnetization curves observed by superconducting quantum interference device magnetometry. Interestingly a noticeable Ga diffusion into the ε-Fe 2 O 3 films has been detected by secondary ion mass spectroscopy providing a clue to the mechanisms guiding the nucleation of exotic metastable epsilon ferrite phase on GaN at high growth temperature and influencing the interfacial properties of the studied films.

Structural and magnetic characterization of Mn/NiFe bilayers with ion-beam-assisted deposition

NASA Astrophysics Data System (ADS)

Wu, Chun-Hsien; Zheng, Chao; Chiu, Chun-Cheng; Manna, Palash Kumar; van Lierop, Johan; Lin, Ko-Wei; Pong, Philip W. T.

2018-01-01

The exchange bias effect in ferromagnetic (FM)/antiferromagnetic (AF) bilayer structures has been widely investigated because its underlying principle is critical for spintronic applications. In this work, the effect of Ar+ beam bombardment on the microstructural and magnetic properties of the Mn/NiFe thin films was investigated. The in-situ Ar+ bombardment nontrivially promoted the Mn/NiFe intermixing and facilitated the formation of the FeMn phase, accompanied by a remarkable reduction of Mn and NiFe layer thickness. The enhanced Mn/NiFe intermixing greatly disordered the interfacial spins, inhibiting the interfacial exchange coupling and giving rise to a significant decrease of the exchange bias field (H ex). The facilitated Mn/NiFe intermixing effect also dramatically degraded the magnetocrystalline anisotropy of the NiFe crystallites, leading to a notable suppression of the coercivity (H c). These results indicate that both the exchange bias and coercivity of the Mn/NiFe bilayers can be directly affected by the in-situ Ar+ bombardment, offering an effective way to modify the magnetism of the exchange-bias systems.

Focus: Structure and dynamics of the interfacial layer in polymer nanocomposites with attractive interactions

DOE PAGES

Cheng, Shiwang; Carroll, Bobby; Bocharova, Vera; ...

2017-03-30

In recent years it has become clear that the interfacial layer formed around nanoparticles in polymer nanocomposites (PNCs) is critical for controlling their macroscopic properties. The interfacial layer occupies a significant volume fraction of the polymer matrix in PNCs and creates strong intrinsic heterogeneity in their structure and dynamics. In this paper, we focus on analysis of the structure and dynamics of the interfacial region in model PNCs with well-dispersed, spherical nanoparticles with attractive interactions. First, we discuss several experimental techniques that provide structural and dynamic information on the interfacial region in PNCs. Then, we discuss the role of variousmore » microscopic parameters in controlling structure and dynamics of the interfacial layer. The analysis presented emphasizes the importance of the polymer-nanoparticle interactions for the slowing down dynamics in the interfacial region, while the thickness of the interfacial layer appears to be dependent on chain rigidity, and has been shown to increase with cooling upon approaching the glass transition. Aside from chain rigidity and polymer-nanoparticle interactions, the interfacial layer properties are also affected by the molecular weight of the polymer and the size of the nanoparticles. Finally, in the last part of this focus article, we emphasize the important challenges in the field of polymer nanocomposites and a potential analogy with the behavior observed in thin films.« less

Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions: Temperature effects using all-atom molecular dynamics simulations.

PubMed

Ou, Shu-Ching; Cui, Di; Wezowicz, Matthew; Taufer, Michela; Patel, Sandeep

2015-06-15

In this study, we examine the temperature dependence of free energetics of nanotube association using graphical processing unit-enabled all-atom molecular dynamics simulations (FEN ZI) with two (10,10) single-walled carbon nanotubes in 3 m NaI aqueous salt solution. Results suggest that the free energy, enthalpy and entropy changes for the association process are all reduced at the high temperature, in agreement with previous investigations using other hydrophobes. Via the decomposition of free energy into individual components, we found that solvent contribution (including water, anion, and cation contributions) is correlated with the spatial distribution of the corresponding species and is influenced distinctly by the temperature. We studied the spatial distribution and the structure of the solvent in different regions: intertube, intratube and the bulk solvent. By calculating the fluctuation of coarse-grained tube-solvent surfaces, we found that tube-water interfacial fluctuation exhibits the strongest temperature dependence. By taking ions to be a solvent-like medium in the absence of water, tube-anion interfacial fluctuation shows similar but weaker dependence on temperature, while tube-cation interfacial fluctuation shows no dependence in general. These characteristics are discussed via the malleability of their corresponding solvation shells relative to the nanotube surface. Hydrogen bonding profiles and tetrahedrality of water arrangement are also computed to compare the structure of solvent in the solvent bulk and intertube region. The hydrophobic confinement induces a relatively lower concentration environment in the intertube region, therefore causing different intertube solvent structures which depend on the tube separation. This study is relevant in the continuing discourse on hydrophobic interactions (as they impact generally a broad class of phenomena in biology, biochemistry, and materials science and soft condensed matter research), and interpretations of hydrophobicity in terms of alternative but parallel signatures such as interfacial fluctuations, dewetting transitions, and enhanced fluctuation probabilities at interfaces. © 2015 Wiley Periodicals, Inc.

Reversible Li-ion conversion reaction for a Ti xGe alloy in a Ti/Ge multilayer

DOE PAGES

Chen, Xiao; Fister, Tim T.; Esbenshade, Jennifer; ...

2017-02-13

Group IV inter-metallics electrochemically alloy with Li with stoichiometries as high as Li 4.4M (M=Si, Ge, Sn or Pb). Furthermore, this provides the second highest known specific capacity (after pure lithium metal) for lithium ion batteries, but the dramatic volume change during cycling greatly limits their use as anodes in Li-ion batteries. We describe an approach to overcome this limitation by constructing electrodes using a Ge/Ti multilayer architecture. In operando X-ray reflectivity and ex situ transmission electron microscopy are used to characterize the hetero-layer structure at various lithium stoichiometries along a lithiation/delithiation cycle. The as-deposited multilayer spontaneously forms a one-dimensionalmore » Ti xGe/Ti/Ti xGe core-shell planar structure embedded in a Ge matrix. The interfacial Ti xGe alloy is observed to be electrochemically active and exhibits reversible phase separation (i.e. a conversion reaction). Including the germanium components, the overall multilayer structure exhibits a 2.3-fold reversible vertical expansion and contraction and is shown to have improved capacity and capacity retention with respect to a Ge film with equivalent active material thickness.« less

Reversible Li-Ion Conversion Reaction for a TixGe Alloy in a Ti/Ge Multilayer.

PubMed

Chen, Xiao; Fister, Tim T; Esbenshade, Jennifer; Shi, Bing; Hu, Xianyi; Wu, Jinsong; Gewirth, Andrew A; Bedzyk, Michael J; Fenter, Paul

2017-03-08

Group IV intermetallics electrochemically alloy with Li with stoichiometries as high as Li 4.4 M (M = Si, Ge, Sn, or Pb). This provides the second highest known specific capacity (after pure lithium metal) for lithium-ion batteries, but the dramatic volume change during cycling greatly limits their use as anodes in Li-ion batteries. We describe an approach to overcome this limitation by constructing electrodes using a Ge/Ti multilayer architecture. In operando X-ray reflectivity and ex situ transmission electron microscopy are used to characterize the heterolayer structure at various lithium stoichiometries along a lithiation/delithiation cycle. The as-deposited multilayer spontaneously forms a one-dimensional Ti x Ge/Ti/Ti x Ge core-shell planar structure embedded in a Ge matrix. The interfacial Ti x Ge alloy is observed to be electrochemically active and exhibits reversible phase separation (i.e., a conversion reaction). Including the germanium components, the overall multilayer structure exhibits a 2.3-fold reversible vertical expansion and contraction and is shown to have improved capacity and capacity retention with respect to a Ge film with equivalent active material thickness.

Hybrid of Co(3)Sn(2)@Co nanoparticles and nitrogen-doped graphene as a lithium ion battery anode.

PubMed

Mahmood, Nasir; Zhang, Chenzhen; Liu, Fei; Zhu, Jinghan; Hou, Yanglong

2013-11-26

A facile strategy was designed for the fabrication of hybrid of Co3Sn2@Co nanoparticles (NPs) and nitrogen-doped graphene (NG) sheets through a hydrothermal synthesis, followed by annealing process. Core-shell architecture of Co3Sn2@Co pin on NG is designed for the dual encapsulation of Co3Sn2 with adaptable ensembles of Co and NG to address the structural and interfacial stability concerns facing tin-based anodes. In the resulted unique architecture of Co3Sn2@Co-NG hybrid, the sealed cobalt cover prevents the direct exposer of Sn with electrolyte because of encapsulated structure and keeps the structural and interfacial integrity of Co3Sn2. However, the elastically strong, flexible and conductive NG overcoat accommodates the volume changes and therefore brings the structural and electrical stabilization of Co3Sn2@Co NPs. As a result, Co3Sn2@Co-NG hybrid exhibits extraordinary reversible capacity of 1615 mAh/g at 250 mA/g after 100 cycles with excellent capacity retention of 102%. The hybrid bears superior rate capability with reversible capacity of 793.9 mAh/g at 2500 mA/g and Coulombic efficiency nearly 100%.

Multifunctional semi-interpenetrating polymer network-nanoencapsulated cathode materials for high-performance lithium-ion batteries.

PubMed

Kim, Ju-Myung; Park, Jang-Hoon; Lee, Chang Kee; Lee, Sang-Young

2014-04-08

As a promising power source to boost up advent of next-generation ubiquitous era, high-energy density lithium-ion batteries with reliable electrochemical properties are urgently requested. Development of the advanced lithium ion-batteries, however, is staggering with thorny problems of performance deterioration and safety failures. This formidable challenge is highly concerned with electrochemical/thermal instability at electrode material-liquid electrolyte interface, in addition to structural/chemical deficiency of major cell components. Herein, as a new concept of surface engineering to address the abovementioned interfacial issue, multifunctional conformal nanoencapsulating layer based on semi-interpenetrating polymer network (semi-IPN) is presented. This unusual semi-IPN nanoencapsulating layer is composed of thermally-cured polyimide (PI) and polyvinyl pyrrolidone (PVP) bearing Lewis basic site. Owing to the combined effects of morphological uniqueness and chemical functionality (scavenging hydrofluoric acid that poses as a critical threat to trigger unwanted side reactions), the PI/PVP semi-IPN nanoencapsulated-cathode materials enable significant improvement in electrochemical performance and thermal stability of lithium-ion batteries.

Multifunctional semi-interpenetrating polymer network-nanoencapsulated cathode materials for high-performance lithium-ion batteries

NASA Astrophysics Data System (ADS)

Kim, Ju-Myung; Park, Jang-Hoon; Lee, Chang Kee; Lee, Sang-Young

2014-04-01

As a promising power source to boost up advent of next-generation ubiquitous era, high-energy density lithium-ion batteries with reliable electrochemical properties are urgently requested. Development of the advanced lithium ion-batteries, however, is staggering with thorny problems of performance deterioration and safety failures. This formidable challenge is highly concerned with electrochemical/thermal instability at electrode material-liquid electrolyte interface, in addition to structural/chemical deficiency of major cell components. Herein, as a new concept of surface engineering to address the abovementioned interfacial issue, multifunctional conformal nanoencapsulating layer based on semi-interpenetrating polymer network (semi-IPN) is presented. This unusual semi-IPN nanoencapsulating layer is composed of thermally-cured polyimide (PI) and polyvinyl pyrrolidone (PVP) bearing Lewis basic site. Owing to the combined effects of morphological uniqueness and chemical functionality (scavenging hydrofluoric acid that poses as a critical threat to trigger unwanted side reactions), the PI/PVP semi-IPN nanoencapsulated-cathode materials enable significant improvement in electrochemical performance and thermal stability of lithium-ion batteries.

Multifunctional semi-interpenetrating polymer network-nanoencapsulated cathode materials for high-performance lithium-ion batteries

PubMed Central

Kim, Ju-Myung; Park, Jang-Hoon; Lee, Chang Kee; Lee, Sang-Young

2014-01-01

As a promising power source to boost up advent of next-generation ubiquitous era, high-energy density lithium-ion batteries with reliable electrochemical properties are urgently requested. Development of the advanced lithium ion-batteries, however, is staggering with thorny problems of performance deterioration and safety failures. This formidable challenge is highly concerned with electrochemical/thermal instability at electrode material-liquid electrolyte interface, in addition to structural/chemical deficiency of major cell components. Herein, as a new concept of surface engineering to address the abovementioned interfacial issue, multifunctional conformal nanoencapsulating layer based on semi-interpenetrating polymer network (semi-IPN) is presented. This unusual semi-IPN nanoencapsulating layer is composed of thermally-cured polyimide (PI) and polyvinyl pyrrolidone (PVP) bearing Lewis basic site. Owing to the combined effects of morphological uniqueness and chemical functionality (scavenging hydrofluoric acid that poses as a critical threat to trigger unwanted side reactions), the PI/PVP semi-IPN nanoencapsulated-cathode materials enable significant improvement in electrochemical performance and thermal stability of lithium-ion batteries. PMID:24710575

Insights into the role of protein molecule size and structure on interfacial properties using designed sequences

PubMed Central

Dwyer, Mirjana Dimitrijev; He, Lizhong; James, Michael; Nelson, Andrew; Middelberg, Anton P. J.

2013-01-01

Mixtures of a large, structured protein with a smaller, unstructured component are inherently complex and hard to characterize at interfaces, leading to difficulties in understanding their interfacial behaviours and, therefore, formulation optimization. Here, we investigated interfacial properties of such a mixed system. Simplicity was achieved using designed sequences in which chemical differences had been eliminated to isolate the effect of molecular size and structure, namely a short unstructured peptide (DAMP1) and its longer structured protein concatamer (DAMP4). Interfacial tension measurements suggested that the size and bulk structuring of the larger molecule led to much slower adsorption kinetics. Neutron reflectometry at equilibrium revealed that both molecules adsorbed as a monolayer to the air–water interface (indicating unfolding of DAMP4 to give a chain of four connected DAMP1 molecules), with a concentration ratio equal to that in the bulk. This suggests the overall free energy of adsorption is equal despite differences in size and bulk structure. At small interfacial extensional strains, only molecule packing influenced the stress response. At larger strains, the effect of size became apparent, with DAMP4 registering a higher stress response and interfacial elasticity. When both components were present at the interface, most stress-dissipating movement was achieved by DAMP1. This work thus provides insights into the role of proteins' molecular size and structure on their interfacial properties, and the designed sequences introduced here can serve as effective tools for interfacial studies of proteins and polymers. PMID:23303222

Removing adsorbed heavy metal ions from sand surfaces via applying interfacial properties of rhamnolipid.

PubMed

Haryanto, Bode; Chang, Chien-Hsiang

2015-01-01

In this study, the interfacial properties of biosurfactant rhamnolipid were investigated and were applied to remove adsorbed heavy metal ions from sand surfaces with flushing operations. The surface tension-lowering activity, micelle charge characteristic, and foaming ability of rhamnolipid were identified first. For rhamnolipid in water, the negatively charged characteristic of micelles or aggregates was confirmed and the foaming ability at concentrations higher than 40 mg/L was evaluated. By using the rhamnolipid solutions in a batch washing approach, the potential of applying the interfacial properties of rhamnolipid to remove adsorbed copper ions from sand surfaces was then demonstrated. In rhamnolipid solution flushing operations for sand-packed medium, higher efficiency was found for the removal of adsorbed copper ions with residual type than with inner-sphere interaction type, implying the important role of interaction type between the copper ion and the sand surface in the removal efficiency. In addition, the channeling effect of rhamnolipid solution flow in the sand-packed medium was clearly observed in the solution flushing operations and was responsible for the low removal efficiency with low contact areas between solution and sand. By using rhamnolipid solution with foam to flush the sand-packed medium, one could find that the channeling effect of the solution flow was reduced and became less pronounced with the increase in the rhamnolipid concentration, or with the enhanced foaming ability. With the reduced channeling effect in the flushing operations, the removal efficiency for adsorbed copper ions was significantly improved. The results suggested that the foam-enhanced rhamnolipid solution flushing operation was efficient in terms of surfactant usage and operation time.

Fundamental aspects of electric double layer force-distance measurements at liquid-solid interfaces using atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Black, Jennifer M.; Zhu, Mengyang; Zhang, Pengfei

In this paper, atomic force microscopy (AFM) force-distance measurements are used to investigate the layered ion structure of Ionic Liquids (ILs) at the mica surface. The effects of various tip properties on the measured force profiles are examined and reveal that the measured ion position is independent of tip properties, while the tip radius affects the forces required to break through the ion layers as well as the adhesion force. Force data is collected for different ILs and directly compared with interfacial ion density profiles predicted by molecular dynamics. Through this comparison it is concluded that AFM force measurements aremore » sensitive to the position of the ion with the larger volume and mass, suggesting that ion selectivity in force-distance measurements are related to excluded volume effects and not to electrostatic or chemical interactions between ions and AFM tip. Finally, the comparison also revealed that at distances greater than 1 nm the system maintains overall electroneutrality between the AFM tip and sample, while at smaller distances other forces (e.g., van der waals interactions) dominate and electroneutrality is no longer maintained.« less

Fundamental aspects of electric double layer force-distance measurements at liquid-solid interfaces using atomic force microscopy

DOE PAGES

Black, Jennifer M.; Zhu, Mengyang; Zhang, Pengfei; ...

2016-09-02

In this paper, atomic force microscopy (AFM) force-distance measurements are used to investigate the layered ion structure of Ionic Liquids (ILs) at the mica surface. The effects of various tip properties on the measured force profiles are examined and reveal that the measured ion position is independent of tip properties, while the tip radius affects the forces required to break through the ion layers as well as the adhesion force. Force data is collected for different ILs and directly compared with interfacial ion density profiles predicted by molecular dynamics. Through this comparison it is concluded that AFM force measurements aremore » sensitive to the position of the ion with the larger volume and mass, suggesting that ion selectivity in force-distance measurements are related to excluded volume effects and not to electrostatic or chemical interactions between ions and AFM tip. Finally, the comparison also revealed that at distances greater than 1 nm the system maintains overall electroneutrality between the AFM tip and sample, while at smaller distances other forces (e.g., van der waals interactions) dominate and electroneutrality is no longer maintained.« less

Origin of the sphere-to-rod transition in cationic micelles with aromatic counterions: specific ion hydration in the interfacial region matters.

PubMed

Geng, Yan; Romsted, Laurence S; Froehner, Sandro; Zanette, Dino; Magid, Linda J; Cuccovia, Iolanda M; Chaimovich, Hernan

2005-01-18

Sphere-to-rod transitions of cetyltrimethylammonium (CTA+) micelles with dichlorobenzoate counterions are remarkably substituent dependent. Simultaneous estimates of the interfacial molarities of H2O, MeOH, and Cl- and 2,6- and 3,5-dichlorobenzoate (2,6OBz and 3,5OBz) counterions were obtained by the chemical trapping method in mixed micelles of CTACl/CTA3,5OBz and CTACl/CTA2,6OBz without added salt. Increasing the CTA3,5OBz mole fraction produces a marked concurrent increase in interfacial 3,5OBz- and a decrease in interfacial H2O concentrations through the sphere-to-rod transition. No abrupt concentration changes are observed with increasing CTA2,6OBz mole fraction. Counterion-specific changes in the interfacial water concentration may be a major contributor to the delicate balance of forces governing micellar morphology.

Porous mixed metal oxides: design, formation mechanism, and application in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wu, Fangfang; Bai, Jing; Feng, Jinkui; Xiong, Shenglin

2015-10-01

The relentless pursuit of new electrode materials for lithium ion batteries (LIBs) has been conducted for decades. Structures with either porous or nanostructure configurations have been confirmed as advantageous candidates for energy storage/conversion applications. The integration of the two features into one structure can provide another chance to improve the electroactivities. Recently, single-phased mixed metal oxides (MMOs) containing different metal cations, in particular, have confirmed high electrochemical activities because of their complex chemical composition, interfacial effects, and the synergic effects of the multiple metal species. In this review, we will focus on recent research advances of MMOs with porous architectures as anode materials in the matter of structural arrangement and compositional manipulation. Moreover, the application of self-supported MMO-based porous structures as LIB anodes is also explained herein. More importantly, investigations on the synthetic system and formation mechanism of porous MMOs will be highlighted. Some future trends for the innovative design of new electrode materials are also discussed in this review. The challenges and prospects will draw many researchers' attention.

Re-examining the tetraphenyl-arsonium/tetraphenyl-borate (TATB) hypothesis for single-ion solvation free energies

NASA Astrophysics Data System (ADS)

Pollard, Travis P.; Beck, Thomas L.

2018-06-01

Attempts to establish an absolute single-ion hydration free energy scale have followed multiple strategies. Two central themes consist of (1) employing bulk pair thermodynamic data and an underlying interfacial-potential-free model to partition the hydration free energy into individual contributions [Marcus, Latimer, and tetraphenyl-arsonium/tetraphenyl-borate (TATB) methods] or (2) utilizing bulk thermodynamic and cluster data to estimate the free energy to insert a proton into water, including in principle an interfacial potential contribution [the cluster pair approximation (CPA)]. While the results for the hydration free energy of the proton agree remarkably well between the three approaches in the first category, the value differs from the CPA result by roughly +10 kcal/mol, implying a value for the effective electrochemical surface potential of water of -0.4 V. This paper provides a computational re-analysis of the TATB method for single-ion free energies using quasichemical theory. A previous study indicated a significant discrepancy between the free energies of hydration for the TA cation and the TB anion. We show that the main contribution to this large computed difference is an electrostatic artifact arising from modeling interactions in periodic boundaries. No attempt is made here to develop more accurate models for the local ion/solvent interactions that may lead to further small free energy differences between the TA and TB ions, but the results clarify the primary importance of interfacial potential effects for analysis of the various free energy scales. Results are also presented, related to the TATB assumption in the organic solvents dimethyl sulfoxide and 1,2-dichloroethane.

Metal/Ion Interactions Induced p–i–n Junction in Methylammonium Lead Triiodide Perovskite Single Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ting; Mukherjee, Rupam; Ovchinnikova, Olga S.

Hybrid perovskites, as emerging multifunctional semiconductors, have demonstrated dual electronic/ionic conduction properties. Here, we report a metal/ion interaction induced p-i-n junction across slightly n-type doped MAPbI 3 single crystals with Au/MAPbI 3/Ag configuration based on interface dependent Seebeck effect, Hall effect and time-of-flight secondary ion mass spectrometry analysis. The organic cations (MA +) interact with Au atoms, forming positively charged coordination complexes at Au/MAPbI 3 interface, whereas iodine anions (I –) can react with Ag contacts, leading to interfacial ionic polarization. Such metal/ion interactions establish a p-doped region near the Au/MAPbI 3 interface due to the formation of MA +more » vacancies, and an n-doped region near the Ag/MAPbI 3 interface due to formation of I – vacancies, consequently forming a p-i-n junction across the crystal in Au/MAPbI 3/Ag configuration. Therefore, the metal/ion interaction plays a role in determining the surface electronic structure and semiconducting properties of hybrid perovskites.« less

Metal/Ion Interactions Induced p–i–n Junction in Methylammonium Lead Triiodide Perovskite Single Crystals

DOE PAGES

Wu, Ting; Mukherjee, Rupam; Ovchinnikova, Olga S.; ...

2017-11-17

Hybrid perovskites, as emerging multifunctional semiconductors, have demonstrated dual electronic/ionic conduction properties. Here, we report a metal/ion interaction induced p-i-n junction across slightly n-type doped MAPbI 3 single crystals with Au/MAPbI 3/Ag configuration based on interface dependent Seebeck effect, Hall effect and time-of-flight secondary ion mass spectrometry analysis. The organic cations (MA +) interact with Au atoms, forming positively charged coordination complexes at Au/MAPbI 3 interface, whereas iodine anions (I –) can react with Ag contacts, leading to interfacial ionic polarization. Such metal/ion interactions establish a p-doped region near the Au/MAPbI 3 interface due to the formation of MA +more » vacancies, and an n-doped region near the Ag/MAPbI 3 interface due to formation of I – vacancies, consequently forming a p-i-n junction across the crystal in Au/MAPbI 3/Ag configuration. Therefore, the metal/ion interaction plays a role in determining the surface electronic structure and semiconducting properties of hybrid perovskites.« less

Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells.

PubMed

Xiao, Minyu; Joglekar, Suneel; Zhang, Xiaoxian; Jasensky, Joshua; Ma, Jialiu; Cui, Qingyu; Guo, L Jay; Chen, Zhan

2017-03-08

A wide variety of charge carrier dynamics, such as transport, separation, and extraction, occur at the interfaces of planar heterojunction solar cells. Such factors can affect the overall device performance. Therefore, understanding the buried interfacial molecular structure in various devices and the correlation between interfacial structure and function has become increasingly important. Current characterization techniques for thin films such as X-ray diffraction, cross section scanning electronmicroscopy, and UV-visible absorption spectroscopy are unable to provide the needed molecular structural information at buried interfaces. In this study, by controlling the structure of the hole transport layer (HTL) in a perovskite solar cell and applying a surface/interface-sensitive nonlinear vibrational spectroscopic technique (sum frequency generation vibrational spectroscopy (SFG)), we successfully probed the molecular structure at the buried interface and correlated its structural characteristics to solar cell performance. Here, an edge-on (normal to the interface) polythiophene (PT) interfacial molecular orientation at the buried perovskite (photoactive layer)/PT (HTL) interface showed more than two times the power conversion efficiency (PCE) of a lying down (tangential) PT interfacial orientation. The difference in interfacial molecular structure was achieved by altering the alkyl side chain length of the PT derivatives, where PT with a shorter alkyl side chain showed an edge-on interfacial orientation with a higher PCE than that of PT with a longer alkyl side chain. With similar band gap alignment and bulk structure within the PT layer, it is believed that the interfacial molecular structural variation (i.e., the orientation difference) of the various PT derivatives is the underlying cause of the difference in perovskite solar cell PCE.

Ionic liquids at the surface of graphite: Wettability and structure

NASA Astrophysics Data System (ADS)

Bordes, Emilie; Douce, Laurent; Quitevis, Edward L.; Pádua, Agílio A. H.; Costa Gomes, Margarida

2018-05-01

The aim of this work is to provide a better understanding of the interface between graphite and different molecular and ionic liquids. Experimental measurements of the liquid surface tension and of the graphite-liquid contact angle for sixteen ionic liquids and three molecular liquids are reported. These experimental values allowed the calculation of the solid/liquid interfacial energy that varies, for the ionic liquids studied, between 14.5 mN m-1 for 1-ethyl-3-methylimidazolium dicyanamide and 37.8 mN m-1 for 3-dodecyl-1-(naphthalen-1-yl)-1H-imidazol-3-ium tetrafluoroborate. Imidazolium-based ionic liquids with large alkyl side-chains or functionalized with benzyl groups seem to interact more favourably with freshly peeled graphite surfaces. Even if the interfacial energy seems a good descriptor to assess the affinity of a liquid for a carbon-based solid material, we conclude that both the surface tension of the liquid and the contact angle between the liquid and the solid can be significant. Molecular dynamics simulations were used to investigate the ordering of the ions near the graphite surface. We conclude that the presence of large alkyl side-chains in the cations increases the ordering of ions at the graphite surface. Benzyl functional groups in the cations lead to a large affinity towards the graphite surface.

Electrochemical Grafting of Graphene Nano Platelets with Aryl Diazonium Salts.

PubMed

Qiu, Zhipeng; Yu, Jun; Yan, Peng; Wang, Zhijie; Wan, Qijin; Yang, Nianjun

2016-10-26

To vary interfacial properties, electrochemical grafting of graphene nano platelets (GNP) with 3,5-dichlorophenyl diazonium tetrafluoroborate (aryl-Cl) and 4-nitrobenzene diazonium tetrafluoroborate (aryl-NO 2 ) was realized in a potentiodynamic mode. The covalently bonded aryl layers on GNP were characterized using atomic force microscopy and X-ray photoelectron spectroscopy. Electrochemical conversion of aryl-NO 2 into aryl-NH 2 was conducted. The voltammetric and impedance behavior of negatively and positively charged redox probes (Fe(CN) 6 3-/4- and Ru(NH 3 ) 6 2+/3+ ) on three kinds of aryl layers grafted on GNP reveal that their interfacial properties are determined by the charge states of redox probes and reactive terminal groups (-Cl, -NO 2 , -NH 2 ) in aryl layers. On aryl-Cl and aryl-NH 2 garted GNP, selective and sensitive monitoring of positively charged lead ions as well as negatively charged nitrite and sulfite ions was achieved, respectively. Such a grafting procedure is thus a perfect way to design and control interfacial properties of graphene.

High Performance Pillared Vanadium Oxide Cathode for Lithium Ion Batteries

DTIC Science & Technology

2015-04-24

As a result, two major approaches have been taken to increase electrode- electrolyte interfacial area while minimizing lithium diffusion lengths...Performance Pillared Vanadium Oxide Cathode for Lithium Ion Batteries Siu on Tung, Krista L. Hawthorne, Yi Ding, James Mainero, and Levi T. Thompson...Automotive Research Development and Engineering Center, Warren, MI 48387, USA Keywords: nanostructured materials, lithium ion batteries, cathode

Molecular Dynamics Simulation of the Structure and Ion Transport in the Ce1 - x Gd x O2 - δ|YSZ Heterosystem

NASA Astrophysics Data System (ADS)

Galin, M. Z.; Ivanov-Schitz, A. K.; Mazo, G. N.

2018-01-01

Molecular dynamics simulation has been used to develop a realistic atomistic model of two-layer Ce1 - x Gd x O2 - δ|YSZ heterosystem. It is shown that Ce1 - x Gd x O2 - δ and YSZ layers (about 15 and 16 Å thick, respectively) retain their crystal structure on the whole. The main structural distortions are found to occur near the Ce1 - x Gd x O2 - δ|YSZ geometric interface, within a narrow interfacial region of few angstroms thick. Both the generalized diffusion characteristics of the system as a whole and the oxygen diffusion coefficients in the layers are calculated, and the diffusion activation energies are determined.

What Can Interfacial Water Molecules Tell Us About Solute Structure?

NASA Astrophysics Data System (ADS)

Willard, Adam

The molecular structure of bulk liquid water reflects a molecular tendency to engage in tetrahedrally coordinated hydrogen bonding. At a solute interface waters preferred three-dimensional hydrogen bonding network must conform to a locally anisotropy interfacial environment. Interfacial water molecules adopt configurations that balance water-solute and water-water interactions. The arrangements of interfacial water molecules, therefore encode information about the effective solute-water interactions. This solute-specific information is difficult to extract, however, because interfacial structure also reflects waters collective response to an anisotropic hydrogen bonding environment. Here I present a methodology for characterizing the molecular-level structure of liquid water interface from simulation data. This method can be used to explore waters static and/or dynamic response to a wide range of chemically and topologically heterogeneous solutes such as proteins.

High surface stability of magnetite on bi-layer Fe3O4/Fe/MgO(0 0 1) films under 1 MeV Kr+ ion irradiation

NASA Astrophysics Data System (ADS)

Kim-Ngan, N.-T. H.; Krupska, M.; Balogh, A. G.; Malinsky, P.; Mackova, A.

2017-12-01

We investigate the stability of the bi-layer Fe3O4/Fe(0 0 1) films grown epitaxially on MgO(0 0 1) substrates with the layer thickness in the range of 25-100 nm upon 1 MeV Kr+ ion irradiation. The layer structure and layer composition of the films before and after ion irradiation were studied by XRR, RBS and RBS-C techniques. The interdiffusion and intermixing was analyzed. No visible change in the RBS spectra was observed upon irradiation with ion fluence below 1015 Kr cm-2. The bi-layer structure and the stoichiometric Fe3O4 layer on the surface were well preserved after Kr+ ion irradiation at low damage levels, although the strong intermixing implied a large interfacial (Fe x O y ) and (Fe, Mg)O y layer respective at Fe3O4-Fe and Fe-MgO interface. The high ion fluence of 3.8  ×  1016 Kr cm-2 has induced a complete oxidization of the buffer Fe layer. Under such Kr fluence, the stoichiometry of the Fe3O4 surface layer was still preserved indicating its high stability. The entire film contains Fe x O y -type composition at ion fluence large than 5.0  ×  1016 Kr cm-2.

New insights into the interface between a single-crystalline metal electrode and an extremely pure ionic liquid: slow interfacial processes and the influence of temperature on interfacial dynamics.

PubMed

Drüschler, Marcel; Borisenko, Natalia; Wallauer, Jens; Winter, Christian; Huber, Benedikt; Endres, Frank; Roling, Bernhard

2012-04-21

Ionic liquids are of high interest for the development of safe electrolytes in modern electrochemical cells, such as batteries, supercapacitors and dye-sensitised solar cells. However, electrochemical applications of ionic liquids are still hindered by the limited understanding of the interface between electrode materials and ionic liquids. In this article, we first review the state of the art in both experiment and theory. Then we illustrate some general trends by taking the interface between the extremely pure ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and an Au(111) electrode as an example. For the study of this interface, electrochemical impedance spectroscopy was combined with in situ STM and in situ AFM techniques. In addition, we present new results for the temperature dependence of the interfacial capacitance and dynamics. Since the interfacial dynamics are characterised by different processes taking place on different time scales, the temperature dependence of the dynamics can only be reliably studied by recording and carefully analysing broadband capacitance spectra. Single-frequency experiments may lead to artefacts in the temperature dependence of the interfacial capacitance. We demonstrate that the fast capacitive process exhibits a Vogel-Fulcher-Tamman temperature dependence, since its time scale is governed by the ionic conductivity of the ionic liquid. In contrast, the slower capacitive process appears to be Arrhenius activated. This suggests that the time scale of this process is determined by a temperature-independent barrier, which may be related to structural reorganisations of the Au surface and/or to charge redistributions in the strongly bound innermost ion layer. This journal is © the Owner Societies 2012

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Mingyuan; Mead, James; Wu, Yueqin

In this study, a nanoindentation-based microcantilever bending technique was utilized to investigate the interfacial properties of a β-Mg{sub 17}Al{sub 12}/AZ91 Mg alloy film/substrate system under tensile loading conditions. Finite element analysis (FEA) was first undertaken to optimise the design of cantilever structures for inducing high tensile stresses at the interface. Cantilevers consisting of a necked region or notch at the interface were determined to be the most successful designs. Microcantilevers containing the β-Mg{sub 17}Al{sub 12}/AZ91 interface were then made using focused ion beam (FIB) milling technique. Necks were made in the cantilevers to intensify the tension at the interface andmore » notches were used to introduce a stress concentration to the interface. During bending, the cantilevers were deflected to failure. Subsequent analysis of the deformed cantilevers using electron microscopies revealed that plastic deformation, and subsequent ductile rupture, of the AZ91 phase was the dominant failure mechanism. When the β-Mg{sub 17}Al{sub 12}/AZ91 film/substrate system was subjected to tension, the softer AZ91 phase failed prior to interfacial delamination, demonstrating that the strength of the interface exceeded the stresses that caused ductile failure in the substrate material. - Highlights: •Microcantilever bending was used to study the property of film/substrate interface. •FEA was used to optimise cantilever design for achieving high interfacial tension. •The intermetallic coatings on AZ91 substrate have strong interfacial adhesion.« less

Water's Interfacial Hydrogen Bonding Structure Reveals the Effective Strength of Surface-Water Interactions.

PubMed

Shin, Sucheol; Willard, Adam P

2018-06-05

We combine all-atom molecular dynamics simulations with a mean field model of interfacial hydrogen bonding to analyze the effect of surface-water interactions on the structural and energetic properties of the liquid water interface. We show that the molecular structure of water at a weakly interacting ( i.e., hydrophobic) surface is resistant to change unless the strength of surface-water interactions are above a certain threshold. We find that below this threshold water's interfacial structure is homogeneous and insensitive to the details of the disordered surface, however, above this threshold water's interfacial structure is heterogeneous. Despite this heterogeneity, we demonstrate that the equilibrium distribution of molecular orientations can be used to quantify the energetic component of the surface-water interactions that contribute specifically to modifying the interfacial hydrogen bonding network. We identify this specific energetic component as a new measure of hydrophilicity, which we refer to as the intrinsic hydropathy.

Bulk and interfacial structures of reline deep eutectic solvent: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Kaur, Supreet; Sharma, Shobha; Kashyap, Hemant K.

2017-11-01

We apply all-atom molecular dynamics simulations to describe the bulk morphology and interfacial structure of reline, a deep eutectic solvent comprising choline chloride and urea in 1:2 molar ratio, near neutral and charged graphene electrodes. For the bulk phase structural investigation, we analyze the simulated real-space radial distribution functions, X-ray/neutron scattering structure functions, and their partial components. Our study shows that both hydrogen-bonding and long-range correlations between different constituents of reline play a crucial role to lay out the bulk structure of reline. Further, we examine the variation of number density profiles, orientational order parameters, and electrostatic potentials near the neutral and charged graphene electrodes with varying electrode charge density. The present study reveals the presence of profound structural layering of not only the ionic components of reline but also urea near the electrodes. In addition, depending on the electrode charge density, the choline ions and urea molecules render different orientations near the electrodes. The simulated number density and electrostatic potential profiles for reline clearly show the presence of multilayer structures up to a distance of 1.2 nm from the respective electrodes. The observation of positive values of the surface potential at zero charge indicates the presence of significant nonelectrostatic attraction between the choline cation and graphene electrode. The computed differential capacitance (Cd) for reline exhibits an asymmetric bell-shaped curve, signifying different variation of Cd with positive and negative surface potentials.

Bulk and interfacial structures of reline deep eutectic solvent: A molecular dynamics study.

PubMed

Kaur, Supreet; Sharma, Shobha; Kashyap, Hemant K

2017-11-21

We apply all-atom molecular dynamics simulations to describe the bulk morphology and interfacial structure of reline, a deep eutectic solvent comprising choline chloride and urea in 1:2 molar ratio, near neutral and charged graphene electrodes. For the bulk phase structural investigation, we analyze the simulated real-space radial distribution functions, X-ray/neutron scattering structure functions, and their partial components. Our study shows that both hydrogen-bonding and long-range correlations between different constituents of reline play a crucial role to lay out the bulk structure of reline. Further, we examine the variation of number density profiles, orientational order parameters, and electrostatic potentials near the neutral and charged graphene electrodes with varying electrode charge density. The present study reveals the presence of profound structural layering of not only the ionic components of reline but also urea near the electrodes. In addition, depending on the electrode charge density, the choline ions and urea molecules render different orientations near the electrodes. The simulated number density and electrostatic potential profiles for reline clearly show the presence of multilayer structures up to a distance of 1.2 nm from the respective electrodes. The observation of positive values of the surface potential at zero charge indicates the presence of significant nonelectrostatic attraction between the choline cation and graphene electrode. The computed differential capacitance (C d ) for reline exhibits an asymmetric bell-shaped curve, signifying different variation of C d with positive and negative surface potentials.

Highly efficient organic light-emitting diodes with a quantum dot interfacial layer.

PubMed

Ryu, Seung Yoon; Hwang, Byoung Har; Park, Ki Wan; Hwang, Hyeon Seok; Sung, Jin Woo; Baik, Hong Koo; Lee, Chang Ho; Song, Seung Yong; Lee, Jun Yeob

2009-02-11

Advanced organic light-emitting diodes (OLEDs), based on a multiple structure, were achieved in combination with a quantum dot (QD) interfacial layer. The authors used core/shell CdSe/ZnS QDs passivated with trioctylphosphine oxide (TOPO) and TOPO-free QDs as interlayers. Multiple-structure OLEDs (MOLEDs) with TOPO-free QDs showed higher device efficiency because of a well-defined interfacial monolayer formation. Additionally, the three-unit MOLED showed high performance for device efficiency with double-structured QD interfacial layers due to the enhanced charge balance and recombination probability.

Cerium reduction at the interface between ceria and yttria-stabilised zirconia and implications for interfacial oxygen non-stoichiometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Kepeng; Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Wenhua Road 72, 110016 Shenyang; Schmid, Herbert

2014-03-01

Epitaxial CeO{sub 2} films with different thickness were grown on Y{sub 2}O{sub 3} stabilised Zirconia substrates. Reduction of cerium ions at the interface between CeO{sub 2} films and yttria stabilised zirconia substrates is demonstrated using aberration-corrected scanning transmission electron microscopy combined with electron energy-loss spectroscopy. It is revealed that most of the Ce ions were reduced from Ce{sup 4+} to Ce{sup 3+} at the interface region with a decay of several nanometers. Several possibilities of charge compensations are discussed. Irrespective of the details, such local non-stoichiometries are crucial not only for understanding charge transport in such hetero-structures but also formore » understanding ceria catalytic properties.« less

Ion-Specific Modulation of Interfacial Interaction Potentials between Solid Substrates and Cell-Sized Particles Mediated via Zwitterionic, Super-Hydrophilic Poly(sulfobetaine) Brushes.

PubMed

Higaki, Yuji; Fröhlich, Benjamin; Yamamoto, Akihisa; Murakami, Ryo; Kaneko, Makoto; Takahara, Atsushi; Tanaka, Motomu

2017-02-16

Zwitterionic polymer brushes draw increasing attention not only because of their superhydrophilic, self-cleaning capability but also due to their excellent antifouling capacity. We investigated the ion-specific modulation of the interfacial interaction potential via densely packed, uniform poly(sulfobetaine) brushes. The vertical Brownian motion of a cell-sized latex particle was monitored by microinterferometry, yielding the effective interfacial interaction potentials V(Δh) and the autocorrelation function of height fluctuation. The potential curvature V″(Δh) exhibited a monotonic increase according to the increase in monovalent salt concentrations, implying the sharpening of the potential confinement. An opposite tendency was observed in CaCl 2 solutions, suggesting that the ion specific modulation cannot be explained by the classical Hofmeister series. When the particle fluctuation was monitored in the presence of free sulfobetaine molecules, the increase in [sulfobetaine] resulted in a distinct increase in hydrodynamic friction. This was never observed in all the other salt solutions, suggesting the interference of zwitterionic pairing of sulfobetaine side chains by the intercalation of sulfobetaine molecules into the brush layer. Furthermore, poly(sulfobetaine) brushes exhibited a very low V″(Δh) and hydrodynamic friction to human erythrocytes, which seems to explain the excellent blood repellency of zwitterionic polymer materials.

Double-plasma enhanced carbon shield for spatial/interfacial controlled electrodes in lithium ion batteries via micro-sized silicon from wafer waste

NASA Astrophysics Data System (ADS)

Chen, Bing-Hong; Chuang, Shang-I.; Duh, Jenq-Gong

2016-11-01

Using spatial and interfacial control, the micro-sized silicon waste from wafer slurry could greatly increase its retention potential as a green resource for silicon-based anode in lithium ion batteries. Through step by step spatial and interfacial control for electrode, the cyclability of recycled waste gains potential performance from its original poor retention property. In the stages of spatial control, the electrode stabilizers of active, inactive and conductive additives were mixed into slurries for maintaining architecture and conductivity of electrode. In addition, a fusion electrode modification of interfacial control combines electrolyte additive, technique of double-plasma enhanced carbon shield (D-PECS) to convert the chemical bond states and to alter the formation of solid electrolyte interphases (SEIs) in the first cycle. The depth profiles of chemical composition from external into internal electrode illustrate that the fusion electrode modification not only forms a boundary to balance the interface between internal and external electrodes but also stabilizes the SEIs formation and soothe the expansion of micro-sized electrode. Through these effect approaches, the performance of micro-sized Si waste electrode can be boosted from its serious capacity degradation to potential retention (200 cycles, 1100 mAh/g) and better meet the requirements for facile and cost-effective in industrial production.

Reduced Capillary Length Scale in the Application of Ostwald Ripening Theory to the Coarsening of Charged Colloidal Crystals in Electrolyte Solutions

NASA Astrophysics Data System (ADS)

Rowe, Jeffrey D.; Baird, James K.

2007-06-01

A colloidal crystal suspended in an electrolyte solution will ordinarily exchange ions with the surrounding solution and develop a net surface charge density and a corresponding double layer. The interfacial tension of the charged surface has contributions arising from: (a) background interfacial tension of the uncharged surface, (b) the entropy associated with the adsorption of ions on the surface, and (c) the polarizing effect of the electrostatic field within the double layer. The adsorption and polarization effects make negative contributions to the surface free energy and serve to reduce the interfacial tension below the value to be expected for the uncharged surface. The diminished interfacial tension leads to a reduced capillary length scale. According to the Ostwald ripening theory of particle coarsening, the reduced capillary length will cause the solute supersaturation to decay more rapidly and the colloidal particles to be smaller in size and greater in number than in the absence of the double layer. Although the length scale for coarsening should be little affected in the case of inorganic colloids, such as AgI, it should be greatly reduced in the case of suspensions of protein crystals, such as apoferritin, catalase, and thaumatin.

Depth profile of halide anions under highly charged biological membrane

NASA Astrophysics Data System (ADS)

Sung, Woongmo; Wang, Wenjie; Lee, Jonggwan; Vaknin, David; Kim, Doseok

2015-03-01

Halide ion (Cl- and I-) distribution under a cationic Langmuir monolayer consisting of 1,2-dipalmitoyl-3 trimethylammonium-propane (DPTAP) molecules was investigated by vibrational sum-frequency generation (VSFG) and X-ray spectroscopy. From VSFG spectra, it was observed that large halide anions (I-) screen surface charge more efficiently so that interfacial water alignment becomes more randomized. On the other hand, number density of ions directly measured by X-ray fluorescence spectroscopy at grazing incidence angle reveals that the ion densities within 6 ~ 8 nm are the same for both I- and Cl-. Since the observed ion densities in both cases are almost equal to the charge density of the DPTAP monolayer, we propose that larger halide anions are attracted closer to the surface making direct binding with the charged headgroups of the molecules in the monolayer, accomplishing charge neutrality in short distance. This direct adsorption of anions also disturbs the monolayer structure both in terms of the conformation of alkyl chains and the vertical configuration of the monolayer, with iodine having the stronger effect. Our study shows that the length scale that ions neutralize a charged interface varies significantly and specifically even between monovalent ions.

Sum Frequency Generation Vibrational Spectroscopy Studies on ModelPeptide Adsorption at the Hydrophobic Solid-Water and HydrophilicSolid-Water Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

York, Roger L.

2007-01-01

Sum frequency generation (SFG) vibrational spectroscopy has been used to study the interfacial structure of several polypeptides and amino acids adsorbed to hydrophobic and hydrophilic surfaces under a variety of experimental conditions. Peptide sequence, peptide chain length, peptide hydrophobicity, peptide side-chain type, surface hydrophobicity, and solution ionic strength all affect an adsorbed peptide's interfacial structure. Herein, it is demonstrated that with the choice of simple, model peptides and amino acids, surface specific SFG vibrational spectroscopy can be a powerful tool to elucidate the interfacial structure of these adsorbates. Herein, four experiments are described. In one, a series of isosequential amphiphilicmore » peptides are synthesized and studied when adsorbed to both hydrophobic and hydrophilic surfaces. On hydrophobic surfaces of deuterated polystyrene, it was determined that the hydrophobic part of the peptide is ordered at the solid-liquid interface, while the hydrophilic part of the peptide appears to have a random orientation at this interface. On a hydrophilic surface of silica, it was determined that an ordered peptide was only observed if a peptide had stable secondary structure in solution. In another experiment, the interfacial structure of a model amphiphilic peptide was studied as a function of the ionic strength of the solution, a parameter that could change the peptide's secondary structure in solution. It was determined that on a hydrophobic surface, the peptide's interfacial structure was independent of its structure in solution. This was in contrast to the adsorbed structure on a hydrophilic surface, where the peptide's interfacial structure showed a strong dependence on its solution secondary structure. In a third experiment, the SFG spectra of lysine and proline amino acids on both hydrophobic and hydrophilic surfaces were obtained by using a different experimental geometry that increases the SFG signal. Upon comparison of these spectra to the SFG spectra of interfacial polylysine and polyproline it was determined that the interfacial structure of a peptide is strongly dependent on its chain length. Lastly, SFG spectroscopy has been extended to the Amide I vibrational mode of a peptide (which is sensitive to peptide secondary structure) by building a new optical parametric amplifier based on lithium thioindate. Evidence is presented that suggests that the interfacial secondary structure of a peptide can be perturbed by a surface.« less

Oxide-Based Composite Electrolytes Using Na3Zr2Si2PO12/Na3PS4 Interfacial Ion Transfer.

PubMed

Noi, Kousuke; Nagata, Yuka; Hakari, Takashi; Suzuki, Kenji; Yubuchi, So; Ito, Yusuke; Sakuda, Atsushi; Hayashi, Akitoshi; Tatsumisago, Masahiro

2018-05-31

All-solid-state sodium batteries using Na 3 Zr 2 Si 2 PO 12 (NASICON) solid electrolytes are promising candidates for safe and low-cost advanced rechargeable battery systems. Although NASICON electrolytes have intrinsically high sodium-ion conductivities, their high sintering temperatures interfere with the immediate development of high-performance batteries. In this work, sintering-free NASICON-based composites with Na 3 PS 4 (NPS) glass ceramics were prepared to combine the high grain-bulk conductivity of NASICON and the interfacial formation ability of NPS. Before the composite preparation, the NASICON/NPS interfacial resistance was investigated by modeling the interface between the NASICON sintered ceramic and the NPS glass thin film. The interfacial ion-transfer resistance was very small above room temperature; the area-specific resistances at 25 and 100 °C were 15.8 and 0.40 Ω cm 2 , respectively. On the basis of this smooth ion transfer, NASICON-rich (70-90 wt %) NASICON-NPS composite powders were prepared by ball-milling fine powders of each component. The composite powders were well-densified by pressing at room temperature. Scanning electron microscopy observation showed highly dispersed sub-micrometer NASICON grains in a dense NPS matrix to form closed interfaces between the oxide and sulfide solid electrolytes. The composite green (unfired) compacts with 70 and 80 wt % NASICON exhibited high total conductivities at 100 °C of 1.1 × 10 -3 and 6.8 × 10 -4 S cm -1 , respectively. An all-solid-state Na 15 Sn 4 /TiS 2 cell was constructed using the 70 wt % NASICON composite electrolyte by the uniaxial pressing of the powder materials, and its discharge properties were evaluated at 100 °C. The cell showed the reversible capacities of about 120 mAh g -1 under the current density of 640 μA cm -2 . The prepared oxide-based composite electrolytes were thus successfully applied in all-solid-state sodium rechargeable batteries without sintering.

Mechanics of finite cracks in dissimilar anisotropic elastic media considering interfacial elasticity

DOE PAGES

Juan, Pierre -Alexandre; Dingreville, Remi

2016-10-31

Interfacial crack fields and singularities in bimaterial interfaces (i.e., grain boundaries or dissimilar materials interfaces) are considered through a general formulation for two-dimensional (2-D) anisotropic elasticity while accounting for the interfacial structure by means of an interfacial elasticity paradigm. The interfacial elasticity formulation introduces boundary conditions that are effectively equivalent to those for a weakly bounded interface. This formalism considers the 2-D crack-tip elastic fields using complex variable techniques. While the consideration of the interfacial elasticity does not affect the order of the singularity, it modifies the oscillatory effects associated with problems involving interface cracks. Constructive or destructive “interferences” aremore » directly affected by the interface structure and its elastic response. Furthermore, this general formulation provides an insight on the physical significance and the obvious coupling between the interface structure and the associated mechanical fields in the vicinity of the crack tip.« less

Mechanics of finite cracks in dissimilar anisotropic elastic media considering interfacial elasticity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juan, Pierre -Alexandre; Dingreville, Remi

Interfacial crack fields and singularities in bimaterial interfaces (i.e., grain boundaries or dissimilar materials interfaces) are considered through a general formulation for two-dimensional (2-D) anisotropic elasticity while accounting for the interfacial structure by means of an interfacial elasticity paradigm. The interfacial elasticity formulation introduces boundary conditions that are effectively equivalent to those for a weakly bounded interface. This formalism considers the 2-D crack-tip elastic fields using complex variable techniques. While the consideration of the interfacial elasticity does not affect the order of the singularity, it modifies the oscillatory effects associated with problems involving interface cracks. Constructive or destructive “interferences” aremore » directly affected by the interface structure and its elastic response. Furthermore, this general formulation provides an insight on the physical significance and the obvious coupling between the interface structure and the associated mechanical fields in the vicinity of the crack tip.« less

To Model Chemical Reactivity in Heterogeneous Emulsions, Think Homogeneous Microemulsions.

PubMed

Bravo-Díaz, Carlos; Romsted, Laurence Stuart; Liu, Changyao; Losada-Barreiro, Sonia; Pastoriza-Gallego, Maria José; Gao, Xiang; Gu, Qing; Krishnan, Gunaseelan; Sánchez-Paz, Verónica; Zhang, Yongliang; Dar, Aijaz Ahmad

2015-08-25

Two important and unsolved problems in the food industry and also fundamental questions in colloid chemistry are how to measure molecular distributions, especially antioxidants (AOs), and how to model chemical reactivity, including AO efficiency in opaque emulsions. The key to understanding reactivity in organized surfactant media is that reaction mechanisms are consistent with a discrete structures-separate continuous regions duality. Aggregate structures in emulsions are determined by highly cooperative but weak organizing forces that allow reactants to diffuse at rates approaching their diffusion-controlled limit. Reactant distributions for slow thermal bimolecular reactions are in dynamic equilibrium, and their distributions are proportional to their relative solubilities in the oil, interfacial, and aqueous regions. Our chemical kinetic method is grounded in thermodynamics and combines a pseudophase model with methods for monitoring the reactions of AOs with a hydrophobic arenediazonium ion probe in opaque emulsions. We introduce (a) the logic and basic assumptions of the pseudophase model used to define the distributions of AOs among the oil, interfacial, and aqueous regions in microemulsions and emulsions and (b) the dye derivatization and linear sweep voltammetry methods for monitoring the rates of reaction in opaque emulsions. Our results show that this approach provides a unique, versatile, and robust method for obtaining quantitative estimates of AO partition coefficients or partition constants and distributions and interfacial rate constants in emulsions. The examples provided illustrate the effects of various emulsion properties on AO distributions such as oil hydrophobicity, emulsifier structure and HLB, temperature, droplet size, surfactant charge, and acidity on reactant distributions. Finally, we show that the chemical kinetic method provides a natural explanation for the cut-off effect, a maximum followed by a sharp reduction in AO efficiency with increasing alkyl chain length of a particular AO. We conclude with perspectives and prospects.

Scalable 2D Mesoporous Silicon Nanosheets for High-Performance Lithium-Ion Battery Anode.

PubMed

Chen, Song; Chen, Zhuo; Xu, Xingyan; Cao, Chuanbao; Xia, Min; Luo, Yunjun

2018-03-01

Constructing unique mesoporous 2D Si nanostructures to shorten the lithium-ion diffusion pathway, facilitate interfacial charge transfer, and enlarge the electrode-electrolyte interface offers exciting opportunities in future high-performance lithium-ion batteries. However, simultaneous realization of 2D and mesoporous structures for Si material is quite difficult due to its non-van der Waals structure. Here, the coexistence of both mesoporous and 2D ultrathin nanosheets in the Si anodes and considerably high surface area (381.6 m 2 g -1 ) are successfully achieved by a scalable and cost-efficient method. After being encapsulated with the homogeneous carbon layer, the Si/C nanocomposite anodes achieve outstanding reversible capacity, high cycle stability, and excellent rate capability. In particular, the reversible capacity reaches 1072.2 mA h g -1 at 4 A g -1 even after 500 cycles. The obvious enhancements can be attributed to the synergistic effect between the unique 2D mesoporous nanostructure and carbon capsulation. Furthermore, full-cell evaluations indicate that the unique Si/C nanostructures have a great potential in the next-generation lithium-ion battery. These findings not only greatly improve the electrochemical performances of Si anode, but also shine some light on designing the unique nanomaterials for various energy devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An electrochemical and structural study of highly uniform tin oxide nanowires fabricated by a novel, scalable solvoplasma technique as anode material for sodium ion batteries

NASA Astrophysics Data System (ADS)

Mukherjee, Santanu; Schuppert, Nicholas; Bates, Alex; Jasinski, Jacek; Hong, Jong-Eun; Choi, Moon Jong; Park, Sam

2017-04-01

A novel solvoplasma based technique was used to fabricate highly uniform SnO2 nanowires (NWs) for application as an anode in sodium-ion batteries (SIBs). This technique is scalable, rapid, and utilizes a rigorous cleaning process to produce very pure SnO2 NWs with enhanced porosity; which improves sodium-ion hosting and reaction kinetics. The batch of NWs obtained from the plasma process were named the "as-made" sample and after cleaning the "pure" sample. Structural characterization showed that the as-made sample has a K+ ion impurity which is absent in the pure samples. The pure samples have a higher maximum specific capacity, 400.71 mAhg-1, and Coulombic efficiency, 85%, compared to the as-made samples which have a maximum specific capacity of 174.69 mAhg-1 and Coulombic efficiency of 74% upon cycling. A study of the electrochemical impedance spectra showed that the as-made samples have a higher interfacial and diffusion resistance than the pure samples and resistances increased after 50 cycles of cell operation for both samples due to progressive electrode degradation. Specific energy vs specific power plots were employed to analyze the performance of the system with respect to the working conditions.

Mechanical, structural and dissolution properties of heat treated thin-film phosphate based glasses

NASA Astrophysics Data System (ADS)

Stuart, Bryan W.; Gimeno-Fabra, Miquel; Segal, Joel; Ahmed, Ifty; Grant, David M.

2017-09-01

Here we show the deposition of 2.7 μm thick phosphate based glass films produced by magnetron sputtering, followed by post heat treatments at 500 °C. Variations in degradation properties pre and post heat treatment were attributed to the formation of Hematite crystals within a glass matrix, iron oxidation and the depletion of hydrophilic P-O-P bonds within the surface layer. As deposited and heat treated coatings showed interfacial tensile adhesion in excess of 73.6 MPa; which surpassed ISO and FDA requirements for HA coatings. Scratch testing of coatings on polished substrates revealed brittle failure mechanisms, amplified due to heat treatment and interfacial failure occurring from 2.3 to 5.0 N. Coatings that were deposited onto sandblasted substrates to mimic commercial implant surfaces, did not suffer from tensile cracking or trackside delamination showing substantial interfacial improvements to between 8.6 and 11.3 N. An exponential dissolution rate was observed from 0 to 2 h for as deposited coatings, which was eliminated via heat treatment. From 2 to 24 h ion release rates ordered P > Na > Mg > Ca > Fe whilst all coatings exhibited linear degradation rates, which reduced by factors of 2.4-3.0 following heat treatments.

Monte Carlo studies on the interfacial properties and interfacial structures of ternary symmetric blends with gradient copolymers.

PubMed

Sun, Dachuan; Guo, Hongxia

2012-08-09

Using Monte Carlo simulation methods, the effects of the comonomer sequence distribution on the interfacial properties (including interfacial tension, interfacial thickness, saturated interfacial area per copolymer, and bending modulus) and interfacial structures (including chain conformations and comonomer distributions of the simulated copolymers at the interfaces) of a ternary symmetric blend containing two immiscible homopolymers and one gradient copolymer are investigated. We find that copolymers with a larger composition gradient width have a broader comonomer distribution along the interface normal, and hence more pronouncedly enlarge the interfacial thickness and reduce the interfacial tension. Furthermore, the counteraction effect, which arises from the tendency of heterogeneous segments in gradient copolymers to phase separate and enter their miscible phases to reduce the local enthalpy, decreases the stretching of copolymers along the interface normal direction. As a result, copolymers with a larger width of gradient composition can occupy a larger interfacial area and form softer monolayers at saturation and are more efficient in facilitating the formation of bicontinuous microemulsions. Additionally, chain length ratio, segregation strength, and interactions between homopolymers and copolymers can alter the interfacial character of gradient copolymers. There exists a strong coupling between the comonomer sequence distribution, chain conformation, and interfacial properties. Especially, bending modulus is mainly determined by the complicated interplay of interfacial copolymer density and interfacial chain conformation.

Towards a unified picture of the water self-ions at the air-water interface: a density functional theory perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baer, Marcel D.; Kuo, I-F W.; Tobias, Douglas J.

2014-07-17

The propensities of the water self ions, H3O+ and OH- , for the air-water interface has implications for interfacial acid-base chemistry. Despite numerous experimental and computational studies, no consensus has been reached on the question of whether or not H3O+ and/or OH- prefer to be at the water surface or in the bulk. Here we report a molecular dynamics simulation study of the bulk vs. interfacial behavior of H3O+ and OH- that employs forces derived from density functional theory with a generalized gradient approximation exchangecorrelation functional (specifically, BLYP) and empirical dispersion corrections. We computed the potential of mean force (PMF)more » for H3O+ as a function of the position of the ion in a 215-molecule water slab. The PMF is flat, suggesting that H3O+ has equal propensity for the air-water interface and the bulk. We compare the PMF for H3O+ to our previously computed PMF for OH- adsorption, which contains a shallow minimum at the interface, and we explore how differences in solvation of each ion at the interface vs. the bulk are connected with interfacial propensity. We find that the solvation shell of H3O+ is only slightly dependent on its position in the water slab, while OH- partially desolvates as it approaches the interface, and we examine how this difference in solvation behavior is manifested in the electronic structure and chemistry of the two ions. DJT was supported by National Science Foundation grant CHE-0909227. CJM was supported by the U.S. Department of Energy‘s (DOE) Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest National Laboratory (PNNL) is operated for the Department of Energy by Battelle. The potential of mean force required resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DEAC05-00OR22725. The remaining simulations and analysis used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. at at Lawrence Berkeley National Laboratory. MDB is grateful for the support of the Linus Pauling Distinguished Postdoctoral Fellowship Program at PNNL.« less

Rational design of hierarchical ZnO@Carbon nanoflower for high performance lithium ion battery anodes

NASA Astrophysics Data System (ADS)

liu, Huichao; Shi, Ludi; Li, Dongzhi; Yu, Jiali; Zhang, Han-Ming; Ullah, Shahid; Yang, Bo; Li, Cuihua; Zhu, Caizhen; Xu, Jian

2018-05-01

The rational structure design and strong interfacial bonding are crucially desired for high performance zinc oxide (ZnO)/carbon composite electrodes. In this context, micro-nano secondary structure design and strong dopamine coating strategies are adopted for the fabrication of flower-like ZnO/carbon (ZnO@C nanoflowers) composite electrodes. The results show the ZnO@C nanoflowers (2-6 μm) are assembled by hierarchical ZnO nanosheets (∼27 nm) and continuous carbon framework. The micro-nano secondary architecture can facilitate the penetration of electrolyte, shorten lithium ions diffusion length, and hinder the aggregation of the nanosheets. Moreover, the strong chemical interaction between ZnO and coating carbon layer via C-Zn bond improves structure stability as well as the electronic conductivity. As a synergistic result, when evaluated as lithium ion batteries (LIBs) anode, the ZnO@C nanoflower electrodes show high reversible capacity of ca. 1200 mA h g-1 at 0.1 A g-1 after 80 cycles. As well as good long-cycling stability (638 and 420 mA h g-1 at 1 and 5 A g-1 after 500 cycles, respectively) and excellent rate capability. Therefore, this rational design of ZnO@C nanoflowers electrode is a promising anode for high-performance LIBs.

Understanding the Interface Dipole of Copper Phthalocyanine (CuPc)/C60: Theory and Experiment.

PubMed

Sai, Na; Gearba, Raluca; Dolocan, Andrei; Tritsch, John R; Chan, Wai-Lun; Chelikowsky, James R; Leung, Kevin; Zhu, Xiaoyang

2012-08-16

Interface dipole determines the electronic energy alignment in donor/acceptor interfaces and plays an important role in organic photovoltaics. Here we present a study combining first principles density functional theory (DFT) with ultraviolet photoemission spectroscopy (UPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) to investigate the interface dipole, energy level alignment, and structural properties at the interface between CuPc and C60. DFT finds a sizable interface dipole for the face-on orientation, in quantitative agreement with the UPS measurement, and rules out charge transfer as the origin of the interface dipole. Using TOF-SIMS, we show that the interfacial morphology for the bilayer CuPc/C60 film is characterized by molecular intermixing, containing both the face-on and the edge-on orientation. The complementary experimental and theoretical results provide both insight into the origin of the interface dipole and direct evidence for the effect of interfacial morphology on the interface dipole.

Study on Silver-plated Molybdenum Interconnected Materials for LEO Solar Cell Array

NASA Astrophysics Data System (ADS)

Zhu, Jia-jun; Hu, Yu-hao; Xu, Meng; Yang, Wu-lin; Fu, Li-cai; Li, De-yi; Zhou, Ling-ping

2017-09-01

Atomic oxygen (AO) is one of the most important environmental factors that affected the performance of low earth orbit spacecraft in orbit. In which, silver was the most common materials as the interconnected materials. However, with the poor AO resistance of silver, the interconnectors could be failure easier, and the lifetime of the spacecraft was also reduced. In this paper, the silver-plated molybdenum interconnected materials made by Ag thin films deposited on the Mo foils by vacuum deposition methods was studied. And the effects of the preparation process on the micro-structure of the Ag thin films, the interfacial adhesive strength and the electrical conductivity of the composites were investigated. It was found that the Ag thin films deposited on the Mo substrates coated the Ag thin films by ion beam assisted deposition(IBAD) methods exhibited a perfectly (200) preferred orientation. The interfacial adhesive strength had been increased to 18.58MPa. And the composites also have excellent electrical performance.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Binzhi; Chopdekar, Rajesh V.; N'Diaye, Alpha T.

The impact of interfacial electronic reconstruction on the magnetic characteristics of La0.7Sr0.3CoO3 (LSCO)/La0.7Sr0.3MnO3 (LSMO) superlattices was investigated as a function of layer thickness using a combination of soft x-ray magnetic spectroscopy and bulk magnetometry. We found that the magnetic properties of the LSCO layers are impacted by two competing electronic interactions occurring at the LSCO/substrate and LSMO/LSCO interfaces. For thin LSCO layers (< 5 nm), the heterostructures exist in a highly coupled state where the chemically distinct layers behave as a single magnetic compound with magnetically active Co2+ ions. As the LSCO thickness increases, a high coercivity LSCO layer developsmore » which biases a low coercivity layer, which is composed not only of the LSMO layer, but also an interfacial LSCO layer. These results suggest a new route to tune the magnetic properties of transition metal oxide heterostructures through careful control of the interface structure.« less

Interfacial microanalysis of rubber tyre-cord adhesion and the influence of cobalt

NASA Astrophysics Data System (ADS)

Fulton, W. Stephen; Smith, Graham C.; Titchener, Keith J.

2004-01-01

The effect of cobalt-containing adhesion promoters on the structure and morphology of rubber-brass and rubber-tyre-cord interfaces before and after ageing has been investigated by X-ray photoelectron spectroscopy (XPS) depth profiling, glancing incidence X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect the cobalt adhesion promoters had upon the interface morphology as they suppressed the growth of crystalline dendrites normally associated with the ageing process was imaged in TEM using samples prepared by the focused ion beam (FIB) milling technique. XPS depth profiling through the interfaces revealed that different types of adhesion promoter influenced the amount and distribution of cobalt ions in the bonding layer. XRD demonstrated the influence that cobalt had upon the structure of the interface and subsequent crystallinity, with a lesser degree of crystallinity being associated with better adhesion performance. From the results a model for the effect of the Co chemistry of the adhesion promotor has been developed.

Schottky barrier at graphene/metal oxide interfaces: insight from first-principles calculations

NASA Astrophysics Data System (ADS)

Cheng, Kai; Han, Nannan; Su, Yan; Zhang, Junfeng; Zhao, Jijun

2017-02-01

Anode materials play an important role in determining the performance of lithium ion batteries. In experiment, graphene (GR)/metal oxide (MO) composites possess excellent electrochemical properties and are promising anode materials. Here we perform density functional theory calculations to explore the interfacial interaction between GR and MO. Our result reveals generally weak physical interactions between GR and several MOs (including Cu2O, NiO). The Schottky barrier height (SBH) in these metal/semiconductor heterostructures are computed using the macroscopically averaged electrostatic potential method, and the role of interfacial dipole is discussed. The calculated SBHs below 1 eV suggest low contact resistance; thus these GR/MO composites are favorable anode materials for better lithium ion batteries.

Schottky barrier at graphene/metal oxide interfaces: insight from first-principles calculations.

PubMed

Cheng, Kai; Han, Nannan; Su, Yan; Zhang, Junfeng; Zhao, Jijun

2017-02-06

Anode materials play an important role in determining the performance of lithium ion batteries. In experiment, graphene (GR)/metal oxide (MO) composites possess excellent electrochemical properties and are promising anode materials. Here we perform density functional theory calculations to explore the interfacial interaction between GR and MO. Our result reveals generally weak physical interactions between GR and several MOs (including Cu2O, NiO). The Schottky barrier height (SBH) in these metal/semiconductor heterostructures are computed using the macroscopically averaged electrostatic potential method, and the role of interfacial dipole is discussed. The calculated SBHs below 1 eV suggest low contact resistance; thus these GR/MO composites are favorable anode materials for better lithium ion batteries.

DNA Nanotechnology-Enabled Interfacial Engineering for Biosensor Development.

PubMed

Ye, Dekai; Zuo, Xiaolei; Fan, Chunhai

2018-06-12

Biosensors represent biomimetic analytical tools for addressing increasing needs in medical diagnosis, environmental monitoring, security, and biodefense. Nevertheless, widespread real-world applications of biosensors remain challenging due to limitations of performance, including sensitivity, specificity, speed, and reproducibility. In this review, we present a DNA nanotechnology-enabled interfacial engineering approach for improving the performance of biosensors. We first introduce the main challenges of the biosensing interfaces, especially under the context of controlling the DNA interfacial assembly. We then summarize recent progress in DNA nanotechnology and efforts to harness DNA nanostructures to engineer various biological interfaces, with a particular focus on the use of framework nucleic acids. We also discuss the implementation of biosensors to detect physiologically relevant nucleic acids, proteins, small molecules, ions, and other biomarkers. This review highlights promising applications of DNA nanotechnology in interfacial engineering for biosensors and related areas.

Hydrated proton and hydroxide charge transfer at the liquid/vapor interface of water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soniat, Marielle; Rick, Steven W., E-mail: srick@uno.edu; Kumar, Revati

2015-07-28

The role of the solvated excess proton and hydroxide ions in interfacial properties is an interesting scientific question with applications in a variety of aqueous behaviors. The role that charge transfer (CT) plays in interfacial behavior is also an unsettled question. Quantum calculations are carried out on clusters of water with an excess proton or a missing proton (hydroxide) to determine their CT. The quantum results are applied to analysis of multi-state empirical valence bond trajectories. The polyatomic nature of the solvated excess proton and hydroxide ion results in directionally dependent CT, depending on whether a water molecule is amore » hydrogen bond donor or acceptor in relation to the ion. With polyatomic molecules, CT also depends on the intramolecular bond distances in addition to intermolecular distances. The hydrated proton and hydroxide affect water’s liquid/vapor interface in a manner similar to monatomic ions, in that they induce a hydrogen-bonding imbalance at the surface, which results in charged surface waters. This hydrogen bond imbalance, and thus the charged waters at the surface, persists until the ion is at least 10 Å away from the interface.« less

Interfacial self-organization of bolaamphiphiles bearing mesogenic groups: relationships between the molecular structures and their self-organized morphologies.

PubMed

Song, Bo; Liu, Guanqing; Xu, Rui; Yin, Shouchun; Wang, Zhiqiang; Zhang, Xi

2008-04-15

This article discusses the relationship between the molecular structure of bolaamphiphiles bearing mesogenic groups and their interfacial self-organized morphology. On the basis of the molecular structures of bolaamphiphiles, we designed and synthesized a series of molecules with different hydrophobic alkyl chain lengths, hydrophilic headgroups, mesogenic groups, and connectors between the alkyl chains and the mesogenic group. Through investigating their interfacial self-organization behavior, some experiential rules are summarized: (1) An appropriate alkyl chain length is necessary to form stable surface micelles; (2) different categories of headgroups have a great effect on the interfacial self-organized morphology; (3) different types of mesogenic groups have little effect on the structure of the interfacial assembly when it is changed from biphenyl to azobenzene or stilbene; (4) the orientation of the ester linker between the mesogenic group and alkyl chain can greatly influence the interfacial self-organization behavior. It is anticipated that this line of research may be helpful for the molecular engineering of bolaamphiphiles to form tailor-made morphologies.

Effects of Helium Ion Irradiation on Properties of Crystalline and Amorphous Multiphase Ceramic Coatings

NASA Astrophysics Data System (ADS)

Chen, Yong; Hu, Liangbin; Qiu, Changjun; He, Bin; Wang, Zhongchang

2017-08-01

The Al2O3-TiO2 crystalline and amorphous multiphase ceramic coatings were prepared on a martensitic steel by laser in situ reaction technique and impose irradiation with 200 keV He ions at different doses. The helium ion irradiation goes 1.55 μm deep from the surface of coating, and the displacement per atom (dpa) for the Al2O3-TiO2 coating is 20.0. When the irradiation fluency is 5 × 1017 ions/cm2, defects are identified in crystalline areas and there form interfacial areas in the coating. These crystal defects tend to migrate and converge at the interfaces. Moreover, helium ion irradiation is found to exert no effect on surface chemical composition and phase constitution of the coatings, while surface mechanical properties for the coatings after irradiation differ from those before irradiation. Further nano-indentation experiments reveal that surface nano-hardness of the Al2O3-TiO2 multiphase coatings decreases as the helium ions irradiation flux increases. Such Al2O3-TiO2 crystalline and amorphous multiphase ceramic coatings exhibit the strongest resistance against helium ion irradiation which shall be applied as candidate structural materials for accelerator-driven sub-critical system to handle the nuclear waste under extreme conditions.

In situ recording of particle network formation in liquids by ion conductivity measurements.

PubMed

Pfaffenhuber, Christian; Sörgel, Seniz; Weichert, Katja; Bele, Marjan; Mundinger, Tabea; Göbel, Marcus; Maier, Joachim

2011-09-21

The formation of fractal silica networks from a colloidal initial state was followed in situ by ion conductivity measurements. The underlying effect is a high interfacial lithium ion conductivity arising when silica particles are brought into contact with Li salt-containing liquid electrolytes. The experimental results were modeled using Monte Carlo simulations and tested using confocal fluorescence laser microscopy and ζ-potential measurements.

Dynamics of Water Associated with Lithium Ions Distributed in Polyethylene Oxide

DOE PAGES

Zhang, Zhe; Ohl, Michael; Diallo, Souleymane O.; ...

2015-11-03

We studied the dynamics of water in polyethylene oxide (PEO)/LiCl solution with quasielastic neutron scattering experiments and molecular dynamics (MD) simulations. Two different time scales of water diffusion representing interfacial water and bulk water dynamics have been identified. Furthermore, the measured diffusion coefficient of interfacial water remained 5–10 times smaller than that of bulk water, but both were slowed by approximately 50% in the presence of Li +. Detailed analysis of MD trajectories suggests that Li + is favorably found at the surface of the hydration layer, and the probability to find the caged Li + configuration formed by themore » PEO is lower than for the noncaged Li +-PEO configuration. In both configurations, however, the slowing down of water molecules is driven by reorienting water molecules and creating water-Li + hydration complexes. Moreover, performing the MD simulation with different ions (Na + and K +) revealed that smaller ionic radius of the ions is a key factor in disrupting the formation of PEO cages by allowing spaces for water molecules to come in between the ion and PEO.« less

Decoupling electron and ion storage and the path from interfacial storage to artificial electrodes

NASA Astrophysics Data System (ADS)

Chen, Chia-Chin; Maier, Joachim

2018-02-01

The requirements for rechargeable batteries place high demands on the electrodes. Efficient storage means accommodating both ions and electrons, not only in substantial amounts, but also with substantial velocities. The materials' space could be largely extended by decoupling the roles of ions and electrons such that transport and accommodation of ions take place in one phase of a composite, and transport and accommodation of electrons in the other phase. Here we discuss this synergistic concept being equally applicable for positive and negative electrodes along with examples from the literature for Li-based and Ag-based cells. Not only does the concept have the potential to mitigate the trade-off between power density and energy density, it also enables a generalized view of bulk and interfacial storage as necessary for nanocrystals. It furthermore allows for testable predictions of heterogeneous storage in passivation layers, dependence of transfer resistance on the state of charge, or heterogeneous storage of hydrogen at appropriate contacts. We also present an outlook on constructing artificial mixed-conductor electrodes that have the potential to achieve both high energy density and high power density.

Dynamics of Water Associated with Lithium Ions Distributed in Polyethylene Oxide

NASA Astrophysics Data System (ADS)

Zhang, Zhe; Ohl, Michael; Diallo, Souleymane O.; Jalarvo, Niina H.; Hong, Kunlun; Han, Youngkyu; Smith, Gregory S.; Do, Changwoo

2015-11-01

The dynamics of water in polyethylene oxide (PEO)/LiCl solution has been studied with quasielastic neutron scattering experiments and molecular dynamics (MD) simulations. Two different time scales of water diffusion representing interfacial water and bulk water dynamics have been identified. The measured diffusion coefficient of interfacial water remained 5-10 times smaller than that of bulk water, but both were slowed by approximately 50% in the presence of Li+ . Detailed analysis of MD trajectories suggests that Li+ is favorably found at the surface of the hydration layer, and the probability to find the caged Li+ configuration formed by the PEO is lower than for the noncaged Li+-PEO configuration. In both configurations, however, the slowing down of water molecules is driven by reorienting water molecules and creating water-Li+ hydration complexes. Performing the MD simulation with different ions (Na+ and K+ ) revealed that smaller ionic radius of the ions is a key factor in disrupting the formation of PEO cages by allowing spaces for water molecules to come in between the ion and PEO.

Dynamics of Water Associated with Lithium Ions Distributed in Polyethylene Oxide.

PubMed

Zhang, Zhe; Ohl, Michael; Diallo, Souleymane O; Jalarvo, Niina H; Hong, Kunlun; Han, Youngkyu; Smith, Gregory S; Do, Changwoo

2015-11-06

The dynamics of water in polyethylene oxide (PEO)/LiCl solution has been studied with quasielastic neutron scattering experiments and molecular dynamics (MD) simulations. Two different time scales of water diffusion representing interfacial water and bulk water dynamics have been identified. The measured diffusion coefficient of interfacial water remained 5-10 times smaller than that of bulk water, but both were slowed by approximately 50% in the presence of Li(+). Detailed analysis of MD trajectories suggests that Li(+) is favorably found at the surface of the hydration layer, and the probability to find the caged Li(+) configuration formed by the PEO is lower than for the noncaged Li(+)-PEO configuration. In both configurations, however, the slowing down of water molecules is driven by reorienting water molecules and creating water-Li(+) hydration complexes. Performing the MD simulation with different ions (Na(+) and K(+)) revealed that smaller ionic radius of the ions is a key factor in disrupting the formation of PEO cages by allowing spaces for water molecules to come in between the ion and PEO.

Structural and Electrochemical Consequences of Al and Ga Cosubstitution in Li7La3Zr2O12 Solid Electrolytes.

PubMed

Rettenwander, Daniel; Redhammer, Günther; Preishuber-Pflügl, Florian; Cheng, Lei; Miara, Lincoln; Wagner, Reinhard; Welzl, Andreas; Suard, Emmanuelle; Doeff, Marca M; Wilkening, Martin; Fleig, Jürgen; Amthauer, Georg

2016-04-12

Several "Beyond Li-Ion Battery" concepts such as all solid-state batteries and hybrid liquid/solid systems envision the use of a solid electrolyte to protect Li-metal anodes. These configurations are very attractive due to the possibility of exceptionally high energy densities and high (dis)charge rates, but they are far from being realized practically due to a number of issues including high interfacial resistance and difficulties associated with fabrication. One of the most promising solid electrolyte systems for these applications is Al or Ga stabilized Li 7 La 3 Zr 2 O 12 (LLZO) based on high ionic conductivities and apparent stability against reduction by Li metal. Nevertheless, the fabrication of dense LLZO membranes with high ionic conductivity and low interfacial resistances remains challenging; it definitely requires a better understanding of the structural and electrochemical properties. In this study, the phase transition from garnet ( Ia 3̅ d , No. 230) to "non-garnet" ( I 4̅3 d , No. 220) space group as a function of composition and the different sintering behavior of Ga and Al stabilized LLZO are identified as important factors in determining the electrochemical properties. The phase transition was located at an Al:Ga substitution ratio of 0.05:0.15 and is accompanied by a significant lowering of the activation energy for Li-ion transport to 0.26 eV. The phase transition combined with microstructural changes concomitant with an increase of the Ga/Al ratio continuously improves the Li-ion conductivity from 2.6 × 10 -4 S cm -1 to 1.2 × 10 -3 S cm -1 , which is close to the calculated maximum for garnet-type materials. The increase in Ga content is also associated with better densification and smaller grains and is accompanied by a change in the area specific resistance (ASR) from 78 to 24 Ω cm 2 , the lowest reported value for LLZO so far. These results illustrate that understanding the structure-properties relationships in this class of materials allows practical obstacles to its utilization to be readily overcome.

Molecular dynamics studies of simple membrane-water interfaces: Structure and functions in the beginnings of cellular life

NASA Technical Reports Server (NTRS)

Pohorille, Andrew; Wilson, Michael A.

1995-01-01

Molecular dynamics computer simulations of the structure and functions of a simple membrane are performed in order to examine whether membranes provide an environment capable of promoting protobiological evolution. Our model membrane is composed of glycerol 1-monooleate. It is found that the bilayer surface fluctuates in time and space, occasionally creating thinning defects in the membrane. These defects are essential for passive transport of simple ions across membranes because they reduce the Born barrier to this process by approximately 40%. Negative ions are transferred across the bilayer more readily than positive ions due to favorable interactions with the electric field at the membrane-water interface. Passive transport of neutral molecules is, in general, more complex than predicted by the solubility-diffusion model. In particular, molecules which exhibit sufficient hydrophilicity and lipophilicity concentrate near membrane surfaces and experience 'interfacial resistance' to transport. The membrane-water interface forms an environment suitable for heterogeneous catalysis. Several possible mechanisms leading to an increase of reaction rates at the interface are discussed. We conclude that vesicles have many properties that make them very good candidates for earliest protocells. Some potentially fruitful directions of experimental and theoretical research on this subject are proposed.

Encapsulation of α-Fe2O3 nanoparticles in graphitic carbon microspheres as high-performance anode materials for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhang, Hongwei; Sun, Xiaoran; Huang, Xiaodan; Zhou, Liang

2015-02-01

A novel ``spray drying-carbonization-oxidation'' strategy has been developed for the fabrication of α-Fe2O3-graphitic carbon (α-Fe2O3@GC) composite microspheres, in which α-Fe2O3 nanoparticles with sizes of 30-50 nm are well-encapsulated by onion-like graphitic carbon shells with a thickness of 5-10 nm. In the constructed composite, the α-Fe2O3 nanoparticles act as the primary active material, providing a high capacity. Meanwhile, the graphitic carbon shells serve as the secondary active component, structural stabilizer, interfacial stabilizer, and electron-highway. As a result, the synthesized α-Fe2O3@GC nanocomposite exhibits a superior lithium-ion battery performance with a high reversible capacity (898 mA h g-1 at 400 mA g-1), outstanding rate capability, and excellent cycling stability. Our product, in terms of the facile and scalable preparation process and excellent electrochemical performance, demonstrates its great potential as a high-performance anode material for lithium-ion batteries.A novel ``spray drying-carbonization-oxidation'' strategy has been developed for the fabrication of α-Fe2O3-graphitic carbon (α-Fe2O3@GC) composite microspheres, in which α-Fe2O3 nanoparticles with sizes of 30-50 nm are well-encapsulated by onion-like graphitic carbon shells with a thickness of 5-10 nm. In the constructed composite, the α-Fe2O3 nanoparticles act as the primary active material, providing a high capacity. Meanwhile, the graphitic carbon shells serve as the secondary active component, structural stabilizer, interfacial stabilizer, and electron-highway. As a result, the synthesized α-Fe2O3@GC nanocomposite exhibits a superior lithium-ion battery performance with a high reversible capacity (898 mA h g-1 at 400 mA g-1), outstanding rate capability, and excellent cycling stability. Our product, in terms of the facile and scalable preparation process and excellent electrochemical performance, demonstrates its great potential as a high-performance anode material for lithium-ion batteries. Electronic supplementary information (ESI) available: XRD pattern, XPS spectrum, CV curves, TEM and SEM images, and table. See DOI: 10.1039/c4nr06771a

Ti2Nb10O29-x mesoporous microspheres as promising anode materials for high-performance lithium-ion batteries

NASA Astrophysics Data System (ADS)

Deng, Shengjue; Luo, Zhibin; Liu, Yating; Lou, Xiaoming; Lin, Chunfu; Yang, Chao; Zhao, Hua; Zheng, Peng; Sun, Zhongliang; Li, Jianbao; Wang, Ning; Wu, Hui

2017-09-01

Ti2Nb10O29 has recently been reported as a promising anode material for lithium-ion batteries. However, its poor electronic conductivity and insufficient Li+-ion diffusion coefficient significantly limit its rate capability. To tackle this issue, a strategy combining nanosizing and crystal-structure modification is employed. Ti2Nb10O29-x mesoporous microspheres with a sphere-size range of 0.5-4 μm are prepared by a one-step solvothermal method followed by thermal treatment in N2. These Ti2Nb10O29-x mesoporous microspheres exhibit primary nanoparticles, a large specific surface area (22.9 m2 g-1) and suitable pore sizes, leading to easy electron/Li+-ion transport and good interfacial reactivity. Ti2Nb10O29-x shows a defective shear ReO3 crystal structure with O2- vacancies and an increased unit cell volume, resulting in its increased Li+-ion diffusion coefficient. Besides Ti4+ and Nb5+ ions, Ti2Nb10O29-x comprises Nb4+ ions with unpaired 4d electrons, which significantly increase its electronic conductivity. As a result of these improvements, the Ti2Nb10O29-x mesoporous microspheres reveal superior electrochemical performances in term of large reversible specific capacity (309 mAh g-1 at 0.1 C), outstanding rate capability (235 mAh g-1 at 40 C) and durable cyclic stability (capacity retention of 92.1% over 100 cycles at 10 C).

Nanoscale Insight and Control of Structural and Electronic Properties of Organic Semiconductor / Metal Interfaces

NASA Astrophysics Data System (ADS)

Maughan, Bret

Organic semiconductor interfaces are promising materials for use in next-generation electronic and optoelectronic devices. Current models for metal-organic interfacial electronic structure and dynamics are inadequate for strongly hybridized systems. This work aims to address this issue by identifying the factors most important for understanding chemisorbed interfaces with an eye towards tuning the interfacial properties. Here, I present the results of my research on chemisorbed interfaces formed between thin-films of phthalocyanine molecules grown on monocrystalline Cu(110). Using atomically-resolved nanoscale imaging in combination with surface-sensitive photoemission techniques, I show that single-molecule level interactions control the structural and electronic properties of the interface. I then demonstrate that surface modifications aimed at controlling interfacial interactions are an effective way to tailor the physical and electronic structure of the interface. This dissertation details a systematic investigation of the effect of molecular and surface functionalization on interfacial interactions. To understand the role of molecular structure, two types of phthalocyanine (Pc) molecules are studied: non-planar, dipolar molecules (TiOPc), and planar, non-polar molecules (H2Pc and CuPc). Multiple adsorption configurations for TiOPc lead to configuration-dependent self-assembly, Kondo screening, and electronic energy-level alignment. To understand the role of surface structure, the Cu(110) surface is textured and passivated by oxygen chemisorption prior to molecular deposition, which gives control over thin-film growth and interfacial electronic structure in H2Pc and CuPc films. Overall, the work presented here demonstrates a method for understanding interfacial electronic structure of strongly hybridized interfaces, an important first step towards developing more robust models for metal-organic interfaces, and reliable, predictive tuning of interfacial properties.

Sulfobetaine as a zwitterionic mediator for 3D hydroxyapatite mineralization

PubMed Central

Liu, Pingsheng; Song, Jie

2013-01-01

Both positively and negatively charged residues play pivotal roles in recruiting precursor ions or ion clusters, and lowering interfacial energy in natural biomineralization process. Synergistic utilization of opposite charges, however, has rarely been implemented in the design of cytocompatible synthetic scaffolds promoting hydroxyapatite (HA)-mineralization and osteointegration. We report the use of cytocompatible zwitterionic sulfobetaine ligands to enable 3-dimensional in vitro mineralization of HA across covalently crosslinked hydrogels. The overall charge-neutral zwitterionic hydrogel effectively recruited oppositely charged precursor ions while overcame excessive swelling exhibited by anionic and cationic hydrogels under physiological conditions, resulting in denser and structurally well-integrated mineralized composites. Further controls over the size, content, and spatial distribution of the mineral domains within the zwitterionic hydrogel are accomplished by facile adjustments of hydrogel crosslinking densities and the supersaturation rate governing heterogeneous mineral nucleation and growth. These findings should inspire many creative uses of zwitterionic polymers and polymer coatings for skeletal tissue repair and regeneration. PMID:23332320

A Self-Binding, Melt-Castable, Crystalline Organic Electrolyte for Sodium Ion Conduction.

PubMed

Chinnam, Parameswara Rao; Fall, Birane; Dikin, Dmitriy A; Jalil, AbdelAziz; Hamilton, Clifton R; Wunder, Stephanie L; Zdilla, Michael J

2016-12-05

The preparation and characterization of the cocrystalline solid-organic sodium ion electrolyte NaClO 4 (DMF) 3 (DMF=dimethylformamide) is described. The crystal structure of NaClO 4 (DMF) 3 reveals parallel channels of Na + and ClO 4 - ions. Pressed pellets of microcrystalline NaClO 4 (DMF) 3 exhibit a conductivity of 3×10 -4  S cm -1 at room temperature with a low activation barrier to conduction of 25 kJ mol -1 . SEM revealed thin liquid interfacial contacts between crystalline grains, which promote conductivity. The material melts gradually between 55-65 °C, but does not decompose, and upon cooling, it resolidifies as solid NaClO 4 (DMF) 3 , permitting melt casting of the electrolyte into thin films and the fabrication of cells in the liquid state and ensuring penetration of the electrolyte between the electrode active particles. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sulfobetaine as a zwitterionic mediator for 3D hydroxyapatite mineralization.

PubMed

Liu, Pingsheng; Song, Jie

2013-03-01

Both positively and negatively charged residues play pivotal roles in recruiting precursor ions or ion clusters, and lowering interfacial energy in natural biomineralization process. Synergistic utilization of opposite charges, however, has rarely been implemented in the design of cytocompatible synthetic scaffolds promoting hydroxyapatite (HA)-mineralization and osteointegration. We report the use of cytocompatible zwitterionic sulfobetaine ligands to enable 3-dimensional in vitro mineralization of HA across covalently crosslinked hydrogels. The overall charge-neutral zwitterionic hydrogel effectively recruited oppositely charged precursor ions while overcame excessive swelling exhibited by anionic and cationic hydrogels under physiological conditions, resulting in denser and structurally well-integrated mineralized composites. Further controls over the size, content, and spatial distribution of the mineral domains within the zwitterionic hydrogel are accomplished by facile adjustments of hydrogel crosslinking densities and the supersaturation rate governing heterogeneous mineral nucleation and growth. These findings should inspire many creative uses of zwitterionic polymers and polymer coatings for skeletal tissue repair and regeneration. Copyright © 2012 Elsevier Ltd. All rights reserved.

Electric-field-induced strain effects on the magnetization of a Pr 0.67Sr 0.33MnO 3 film

DOE PAGES

Zhang, B.; Sun, C. -J.; Lu, W.; ...

2015-05-26

The electric-field control of magnetic properties of Pr 0.67Sr 0.33MnO 3 (PSMO) film on piezoelectric Pb(Mg 1/3Nb 2/3)O 3-PbTiO 3 (PMNT) substrate was investigated. The piezoelectric response of the PMNT substrate to the electric field produced strain that was coupled to the PSMO film. The in-plane compressive (tensile) strain increased (decreased) the magnetization. The change of magnetic moment was associated with the Mn ions. First principle simulations showed that the strain-induced electronic redistribution of the two e g orbitals (3d z 2 and 3d x 2 -y 2) of Mn ions was responsible for the change of magnetic moment. Thismore » work demonstrates that the magnetoelectric effect in manganite/piezoelectric hetero-structures originates from the change in eg orbital occupancy of Mn ions induced by strain rather than the interfacial effect.« less

Low energy dislocation structures in epitaxy

NASA Technical Reports Server (NTRS)

Van Der Merwe, Jan H.; Woltersdorf, J.; Jesser, W. A.

1986-01-01

The principle of minimum energy was applied to epitaxial interfaces to show the interrelationship beteen misfit, overgrowth thickness and misfit dislocation spacing. The low energy dislocation configurations were presented for selected interfacial geometries. A review of the interfacial energy calculations was made and a critical assessment of the agreement between theory and experiment was presented. Modes of misfit accommodation were presented with emphasis on the distinction between kinetic effects and equilibrium conditions. Two-dimensional and three-dimensional overgrowths were treated together with interdiffusion-modified interfaces, and several models of interfacial structure were treated including the classical and the current models. The paper is concluded by indicating areas of needed investigation into interfacial structure.

Transition metal impurities in the solid electrolyte LLZO (Li7La3Zr2O12) : Transport rates and their impact on Li-ion mobility

NASA Astrophysics Data System (ADS)

Yang, Sheng; Siegel, Donald

LLZO has many properties of an ideal solid electrolyte in lithium-ion batteries since it could enable the use of high voltage electrodes and hence enhance the energy density of lithium ion batteries. With supervalent cation doping such as Al3+, Ga3+ on the Li-site, the room temperature ionic conductivity of the cubic LLZO can accomplish high ionic conductivity up to 1mS/cm. However, some experiments suggest that mutual diffusion layers were formed between LLZO and cathode where transition metal (TM) diffused into LLZO, which could possibly lead to large interfacial resistance. In this study, we quantified the performance of LLZO after doping with cobalt, manganese, iron and nickel. In particular, we used molecular dynamics simulations with empirical Morse-type potentials to investigate the TM transport rates and their impact on Li-ion mobility. Our work indicates that TM impurities diffuse slower than Li-ion and they will result in a decrease in the Li-ion mobility by blocking Li-ion pathways. Our work shines light on the origin of interfacial resistance between LLZO and different cathodes. This work was supported by U.S. Department Energy's U.S.- China Clean Energy Research Center Clean Vehicles Consortium (CERC CVC), Grant No. DE-PI0000012.

Two-Step Adsorption of PtCl 6 2– Complexes at a Charged Langmuir Monolayer: Role of Hydration and Ion Correlations

DOE PAGES

Uysal, Ahmet; Rock, William; Qiao, Baofu; ...

2017-11-03

Anion exchange at positively charged interfaces plays an important role in a variety of physical and chemical processes. However, the molecular-scale details of these processes, especially with heavy and large anionic complexes, are not well-understood. Here, we studied the adsorption of PtCl 6 2– anionic complexes to floating DPTAP monolayers in the presence of excess Cl– as a function of the bulk chlorometalate concentration. This system aims to simulate the industrial conditions for heavy metal separations with solvent extraction. In situ X-ray scattering and fluorescence measurements, which are element and depth sensitive, show that the chlorometalate ions only adsorb inmore » the diffuse layer at lower concentrations, while they adsorb predominantly in the Stern layer at higher concentrations. The response of DPTAP molecules to the adsorbed ions is determined independently by grazing incidence X-ray diffraction and supports this picture. Molecular dynamics simulations further elucidate the nanoscale structure of the interfacial complexes. The results suggest that ion hydration and ion–ion correlations play a key role in the competitive adsorption process.« less

Redesigning Channel-Forming Peptides: Amino Acid Substitutions that Enhance Rates of Supramolecular Self-Assembly and Raise Ion Transport Activity

PubMed Central

Shank, Lalida P.; Broughman, James R.; Takeguchi, Wade; Cook, Gabriel; Robbins, Ashley S.; Hahn, Lindsey; Radke, Gary; Iwamoto, Takeo; Schultz, Bruce D.; Tomich, John M.

2006-01-01

Three series of 22-residue peptides derived from the transmembrane M2 segment of the glycine receptor α1-subunit (M2GlyR) have been designed, synthesized, and tested to determine the plasticity of a channel-forming sequence and to define whether channel pores with enhanced conductive properties could be created. Sixteen sequences were examined for aqueous solubility, solution-association tendency, secondary structure, and half-maximal concentration for supramolecular assembly, channel activity, and ion transport properties across epithelial monolayers. All peptides interact strongly with membranes: associating with, inserting across, and assembling to form homooligomeric bundles when in micromolar concentrations. Single and double amino acid replacements involving arginine and/or aromatic amino acids within the final five C-terminal residues of the peptide cause dramatic effects on the concentration dependence, yielding a range of K1/2 values from 36 ± 5 to 390 ± 220 μM for transport activity. New water/lipid interfacial boundaries were established for the transmembrane segment using charged or aromatic amino acids, thus limiting the peptides' ability to move perpendicularly to the plane of the bilayer. Formation of discrete water/lipid interfacial boundaries appears to be necessary for efficient supramolecular assembly and high anion transport activity. A peptide sequence is identified that may show efficacy in channel replacement therapy for channelopathies such as cystic fibrosis. PMID:16387776

Molecular simulation study of dynamical properties of room temperature ionic liquids with carbon pieces

DOE PAGES

Feng, Guang; Zhao, Wei; Cummings, Peter T.; ...

2016-03-29

Room temperature ionic liquids (RTILs) with dispersed carbon pieces exhibit distinctive physiochemical properties. In order to explore the molecular mechanism, RTILs/carbon pieces mixture we investigated it by molecular dynamics (MD) simulation in this work. Rigid and flexible carbon pieces in the form of graphene with different thicknesses and carbon nanotubes in different sizes were dispersed in a representative RTIL 1-butyl-3-methyl-imidazolium dicyanamide ([Bmim][DCA]). Our study demonstrated that the diffusion coefficients of RTILs in the presence of flexible carbons are similar to those of bulk RTILs at varying temperatures, which is in contrast to the decreased diffusion of RTILs in the presencemore » of rigid carbons. In addition, interfacial ion number density at rigid carbon surfaces was higher than that at flexible ones, which is correlated with the accessible external surface area of carbon pieces. The life time of cation-anion pair in the presence of carbon pieces also exhibited a dependence on carbon flexibility. RTILs with dispersed rigid carbon pieces showed longer ion pair life time than those with flexible ones, in consistence with the observation in diffusion coefficients. Furthermore, this work highlights the necessity of including the carbon flexibility when performing MD simulation of RTILs in the presence of dispersed carbon pieces in order to obtain the reliable dynamical and interfacial structural properties.« less

Ion-Specific Interfacial Crystallization of Polymer-Grafted Nanoparticles

DOE PAGES

Zhang, Honghu; Wang, Wenjie; Mallapragada, Surya; ...

2017-06-27

In this study, ion-specific effects on the assembly and crystallization of polyethylene-glycol-grafted Au nanoparticles (PEG-AuNPs) at the vapor–liquid interface are examined by surface sensitive synchrotron X-ray scattering methods. We show that monovalent salts, such as KCl and NaCl, that do not advance phase separation of pure PEG at room temperature induce two-dimensional (2D) self-assembly and crystallization of PEG-AuNPs with some distinctions. Whereas for KCl the 2D hexagonal coherence length of the PEG-AuNP superlattices is remarkably large compared to other salts (over micron-sized crystalline grains), NaCl induces coexistence of two hexagonal structures. Using various salts, we find that the value ofmore » the lattice constant is correlated to the ionic hydration entropy consistent with the Hofmeister series.« less

Impact of electrically formed interfacial layer and improved memory characteristics of IrOx/high-κx/W structures containing AlOx, GdOx, HfOx, and TaOx switching materials.

PubMed

Prakash, Amit; Maikap, Siddheswar; Banerjee, Writam; Jana, Debanjan; Lai, Chao-Sung

2013-09-06

Improved switching characteristics were obtained from high-κ oxides AlOx, GdOx, HfOx, and TaOx in IrOx/high-κx/W structures because of a layer that formed at the IrOx/high-κx interface under external positive bias. The surface roughness and morphology of the bottom electrode in these devices were observed by atomic force microscopy. Device size was investigated using high-resolution transmission electron microscopy. More than 100 repeatable consecutive switching cycles were observed for positive-formatted memory devices compared with that of the negative-formatted devices (only five unstable cycles) because it contained an electrically formed interfacial layer that controlled 'SET/RESET' current overshoot. This phenomenon was independent of the switching material in the device. The electrically formed oxygen-rich interfacial layer at the IrOx/high-κx interface improved switching in both via-hole and cross-point structures. The switching mechanism was attributed to filamentary conduction and oxygen ion migration. Using the positive-formatted design approach, cross-point memory in an IrOx/AlOx/W structure was fabricated. This cross-point memory exhibited forming-free, uniform switching for >1,000 consecutive dc cycles with a small voltage/current operation of ±2 V/200 μA and high yield of >95% switchable with a large resistance ratio of >100. These properties make this cross-point memory particularly promising for high-density applications. Furthermore, this memory device also showed multilevel capability with a switching current as low as 10 μA and a RESET current of 137 μA, good pulse read endurance of each level (>105 cycles), and data retention of >104 s at a low current compliance of 50 μA at 85°C. Our improvement of the switching characteristics of this resistive memory device will aid in the design of memory stacks for practical applications.

Ordered water structure at hydrophobic graphite interfaces observed by 4D, ultrafast electron crystallography

PubMed Central

Yang, Ding-Shyue; Zewail, Ahmed H.

2009-01-01

Interfacial water has unique properties in various functions. Here, using 4-dimensional (4D), ultrafast electron crystallography with atomic-scale spatial and temporal resolution, we report study of structure and dynamics of interfacial water assembly on a hydrophobic surface. Structurally, vertically stacked bilayers on highly oriented pyrolytic graphite surface were determined to be ordered, contrary to the expectation that the strong hydrogen bonding of water on hydrophobic surfaces would dominate with suppressed interfacial order. Because of its terrace morphology, graphite plays the role of a template. The dynamics is also surprising. After the excitation of graphite by an ultrafast infrared pulse, the interfacial ice structure undergoes nonequilibrium “phase transformation” identified in the hydrogen-bond network through the observation of structural isosbestic point. We provide the time scales involved, the nature of ice-graphite structural dynamics, and relevance to properties related to confined water. PMID:19246378

Understanding the liquid-liquid (water-hexane) interface

NASA Astrophysics Data System (ADS)

Murad, Sohail; Puri, Ishwar K.

2017-10-01

Nonequilibrium molecular dynamics simulations are employed to investigate the interfacial thermal resistance of nanoscale hexane-water interfaces subject to an applied heat flux. Our studies show that these liquid-liquid interfaces exhibit behavior significantly dissimilar to that of solid-liquid and solid-vapor interfaces. Notably, the thermal resistance of a hexane-water interface is contingent on the interfacial temperature gradient alone with negligible dependence on the mean interfacial temperature, while the solid-liquid dependent strongly on the interfacial temperature. Application of a heat flux also increases the interface thickness significantly as compared to an equilibrium isothermal interface. Since liquid-liquid interfaces have been proposed for diverse applications, e.g., sensors for wastewater treatment and for extraction of toxic ions from water, they can be designed to be wider by applying a heat flux. This may allow the interface to be used for other applications not possible currently because of the very limited thickness of the interface in isothermal systems.

Interfacial water on crystalline silica: a comparative molecular dynamics simulation study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Tuan A.; Argyris, Dimitrios; Papavassiliou, Dimitrios V.

2011-03-03

All-atom molecular dynamics simulations were conducted to study the dynamics of aqueous electrolyte solutions confined in slit-shaped silica nanopores of various degrees of protonation. Five degrees of protonation were prepared by randomly removing surface hydrogen atoms from fully protonated crystalline silica surfaces. Aqueous electrolyte solutions containing NaCl or CsCl salt were simulated at ambient conditions. In all cases, the ionic concentration was 1 M. The results were quantified in terms of atomic density distributions within the pores, and the self-diffusion coefficient along the direction parallel to the pore surface. We found evidence for ion-specific properties that depend on ion surface,more » water ion, and only in some cases ion ion correlations. The degree of protonation strongly affects the structure, distribution, and the dynamic behavior of confined water and electrolytes. Cl ions adsorb on the surface at large degrees of protonation, and their behavior does not depend significantly on the cation type (either Na+ or Cs+ ions are present in the systems considered). The cations show significant ion-specific behavior. Na+ ions occupy different positions within the pore as the degree of protonation changes, while Cs+ ions mainly remain near the pore center at all conditions considered. For a given degree of protonation, the planar self-diffusion coefficient of Cs+ is always greater than that of Na+ ions. The results are useful for better understanding transport under confinement, including brine behavior in the subsurface, with important applications such as environmental remediation.« less

Interfacial activity in alkaline flooding enhanced oil recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chan, M.K.

1981-01-01

The ionization of long-chained organic acids in the crude oil to form soaps was shown to be primarily responsible for the lowering of oil-water interfacial tension at alkaline pH. These active acids can be concentrated by silica gel chromatography into a minor polar fraction. An equilibrium chemical model was proposed based on 2 competing reactions: the ionization of acids to form active anions, and the formation of undissociated soap between acid anions and sodium ions. It correlates the interfacial activity with the interfacial concentration of active acid anions which is expressed in terms of the concentrations of the chemical speciesmore » in the system. The model successfully predicts the observed oil-alkaline solution interfacial phenomenon, including its dependence on pH, alkali and salt concentrations, type of acid present and type of soap formed. Flooding at different alkali concentrations to activate different acid species present in the crude was shown to give better recovery than flooding at a single high alkali concentration. Treating the crude oil with a dilute solution of mineral acids liberates additional free active acids and yields better interfacial activity during subsequent alkali contact.« less

Effect of 100 MeV Si7+ ions' irradiation on Pd/n-GaAs Schottky diodes

NASA Astrophysics Data System (ADS)

Sinha, O. P.

2017-12-01

Pd/n-GaAs realized devices (junction made on a virgin substrate prior to irradiation) and Pd/n-GaAs fabricated devices (junction realized after the virgin substrate irradiation) have been irradiated with 100 MeV Si7+ ions for the varying fluence of 1012-1013 ions/cm2. The devices have been characterized by I-V and C-V techniques for an electrical response. The electrical characterization of these devices shows the presence of interfacial layer. Moreover, the C-V characteristics show strong frequency dependence behavior, which indicates the involvement of interfacial charge layer with deep electron states. The hydrogenation of these devices has not caused any significant change in the electrical (I-V and C-V) characteristics. The observed results have been discussed in the realm of radiation-induced defects, which cause the carrier removal and compensation phenomena to cause the observed high resistivity and filling and unfilling of these traps' level to cause strong frequency dependence behavior.

Nanoscale interfacial defect shedding in a growing nematic droplet.

PubMed

Gurevich, Sebastian; Provatas, Nikolas; Rey, Alejandro

2017-08-01

Interfacial defect shedding is the most recent known mechanism for defect formation in a thermally driven isotropic-to-nematic phase transition. It manifests in nematic-isotropic interfaces going through an anchoring switch. Numerical computations in planar geometry established that a growing nematic droplet can undergo interfacial defect shedding, nucleating interfacial defect structures that shed into the bulk as +1/2 point defects. By extending the study of interfacial defect shedding in a growing nematic droplet to larger length and time scales, and to three dimensions, we unveil an oscillatory growth mode involving shape and anchoring transitions that results in a controllable regular distributions of point defects in planar geometry, and complex structures of disclination lines in three dimensions.

Bioinspired design and interfacial failure of biomedical systems

NASA Astrophysics Data System (ADS)

Rahbar, Nima

The deformation mechanism of nacre as a model biological material is studied in this project. A numerical model is presented which consists of tensile pillars, shear pillars, asperities and aragonite platelets. It has been shown that the tensile pillars are the main elements that control the global stiffness of the nacre structure. Meanwhile, ultimate strength of the nacre structure is controlled by asperities and their behavior and the ratio of L/2D which is itself a function of the geometry of the platelets. Protein/shear pillars provide the glue which holds the assembly of entire system together, particularly in the direction normal to the platelets main axis. This dissertation also presents the results of a combined theoretical/computational and experimental effort to develop crack resistant dental multilayers that are inspired by the functionally graded dento-enamel junction (DEJ) structure that occurs between dentin and enamel in natural teeth. The complex structures of natural teeth and ceramic crowns are idealized using at layered configurations. The potential effects of occlusal contact are then modeled using finite element simulations of Hertzian contact. The resulting stress distributions are compared for a range of possible bioinspired, functionally graded architecture. The computed stress distributions show that the highest stress concentrations in the top ceramic layer of crown structures are reduced significantly by the use of bioinspired functionally graded architectures. The reduced stresses are shown to be associated with significant improvements (30%) in the pop-in loads over a wide range of clinically-relevant loading rates. The implications of the results are discussed for the design of bioinspired dental ceramic crown structures. The results of a combined experimental and computational study of mixed mode fracture in glass/cement and zirconia/cement interfaces that are relevant to dental restorations is also presented. The interfacial fracture is investigated using Brazil-nut specimens. The kinking in-and-out of the interface that occurs between glass/cement and zirconia/cement interfaces, is also shown to be consistent with predictions from a microstructure-based finite element model. The predictions are later verified using focused ion beam and scanning electron microscopy images. Finally, the adhesion between layers that are relevant to drug-eluting stents is explored. Brazil disk specimens were used to measure the interfacial fracture energies between the layers of a model drug eluting stent over a wide range of mode mixities. The trends in the overall fracture energies are predicted using a combination of adhesion theories and fracture mechanics concepts. The measured interfacial fracture energies are shown to be in good agreement with the predictions.

Deformation twinning in a creep-deformed nanolaminate structure

NASA Astrophysics Data System (ADS)

Hsiung, Luke L.

2010-10-01

The underlying mechanism of deformation twinning occurring in a TiAl-(γ)/Ti3Al-(α2) nanolaminate creep deformed at elevated temperatures has been studied. Since the multiplication and propagation of lattice dislocations in both γ and α2 thin lamellae are very limited, the total flow of lattice dislocations becomes insufficient to accommodate the accumulated creep strains. Consequently, the movement of interfacial dislocations along the laminate interfaces, i.e., interface sliding, becomes an alternative deformation mode of the nanolaminate structure. Pile-ups of interfacial dislocations occur when interfacial ledges and impinged lattice dislocations act as obstacles to impede the movement of interfacial dislocations. Deformation twinning can accordingly take place to relieve a stress concentration resulting from the pile-up of interfacial dislocations. An interface-controlled twinning mechanism driven by the pile-up and dissociation of interfacial dislocations is accordingly proposed.

Engineering Pt/Pd Interfacial Electronic Structures for Highly Efficient Hydrogen Evolution and Alcohol Oxidation.

PubMed

Fan, Jinchang; Qi, Kun; Zhang, Lei; Zhang, Haiyan; Yu, Shansheng; Cui, Xiaoqiang

2017-05-31

Tailoring the interfacial structure of Pt-based catalysts has emerged as an effective strategy to improve catalytic activity. However, little attention has been focused on investigating the relationship between the interfacial facets and their catalytic activity. Here, we design and implement Pd-Pt interfaces with controlled heterostructure features by epitaxially growing Pt nanoparticles on Pd nanosheets. On the basis of both density functional theory calculation and experimental results, we demonstrate that charge transfer from Pd to Pt is highly dependent on the interfacial facets of Pd substrates. Therefore, the Pd-Pt heterostructure with Pd(100)-Pt interface exhibits excellent activity and long-term stability for hydrogen evolution and methanol/ethanol oxidation reactions in alkaline medium, much better than that with Pd (111)-Pt interface or commercial Pt/C. Interfacial crystal facet-dependent electronic structural modulation sheds a light on the design and investigation of new heterostructures for high-activity catalysts.

Carbon-Coated Current Collectors for High-Power Li-Ion Secondary Batteries

DTIC Science & Technology

2012-08-29

deposition condition. Surface analysis indicates that this thin C layer does not contain interfacial Al-carbide layer. LiFePO4 electrode using this C...layer does not contain an interfacial Al-carbide layer. LiFePO4 electrode using this C-coated Al current collector exhibits higher capacity under 10 C...cathode. LiFePO4 (LFPO) was used as active materials for test, and this cathode material was purchased from Aleees company. The LFPO active layer

A discontinuous Poisson-Boltzmann equation with interfacial jump: homogenisation and residual error estimate.

PubMed

Fellner, Klemens; Kovtunenko, Victor A

2016-01-01

A nonlinear Poisson-Boltzmann equation with inhomogeneous Robin type boundary conditions at the interface between two materials is investigated. The model describes the electrostatic potential generated by a vector of ion concentrations in a periodic multiphase medium with dilute solid particles. The key issue stems from interfacial jumps, which necessitate discontinuous solutions to the problem. Based on variational techniques, we derive the homogenisation of the discontinuous problem and establish a rigorous residual error estimate up to the first-order correction.

Structural match of heterogeneously nucleated Mn(OH) 2(s) nanoparticles on quartz under various pH conditions

DOE PAGES

Jung, Haesung; Lee, Byeongdu; Jun, Young -Shin

2016-09-14

The early nucleation stage of Mn (hydr)oxide on mineral surfaces is crucial to understand its occurrence and the cycling of nutrients in environmental systems. However, there are only limited studies on the heterogeneous nucleation of Mn(OH) 2(s) as the initial stage of Mn (hydr)oxide precipitation. Here, we investigated the effect of pH on the initial nucleation of Mn(OH) 2(s) on quartz. Under various pH conditions of 9.8, 9.9, and 10.1, we analyzed the structural matches between quartz and heterogeneously nucleated Mn(OH) 2(s). The structural matches were calculated by measuring lateral and vertical dimensions using grazing incidence small angle X-ray scatteringmore » (GISAXS) and atomic force microscopy (AFM), respectively. We found that a poorer structural match occurred at a higher pH than at a lower pH. The faster nucleation at a higher pH condition accounted for the observed poorer structural match. By fitting the structural match using classical nucleation theory, we also calculated the interfacial energy between Mn(OH) 2(s) and water (γ nf = 71 ± 7 mJ/m 2). The calculated m values and γ nf provided the variance of interfacial energy between quartz and Mn(OH) 2(s): γ sn = 262–272 mJ/m 2. As a result, this study provides new qualitative and quantitative information about heterogeneous nucleation on environmentally an abundant mineral surface, quartz, and it offers important underpinnings for understanding the fate and transport of trace ions in environmental systems.« less

Structural match of heterogeneously nucleated Mn(OH) 2(s) nanoparticles on quartz under various pH conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Haesung; Lee, Byeongdu; Jun, Young -Shin

The early nucleation stage of Mn (hydr)oxide on mineral surfaces is crucial to understand its occurrence and the cycling of nutrients in environmental systems. However, there are only limited studies on the heterogeneous nucleation of Mn(OH) 2(s) as the initial stage of Mn (hydr)oxide precipitation. Here, we investigated the effect of pH on the initial nucleation of Mn(OH) 2(s) on quartz. Under various pH conditions of 9.8, 9.9, and 10.1, we analyzed the structural matches between quartz and heterogeneously nucleated Mn(OH) 2(s). The structural matches were calculated by measuring lateral and vertical dimensions using grazing incidence small angle X-ray scatteringmore » (GISAXS) and atomic force microscopy (AFM), respectively. We found that a poorer structural match occurred at a higher pH than at a lower pH. The faster nucleation at a higher pH condition accounted for the observed poorer structural match. By fitting the structural match using classical nucleation theory, we also calculated the interfacial energy between Mn(OH) 2(s) and water (γ nf = 71 ± 7 mJ/m 2). The calculated m values and γ nf provided the variance of interfacial energy between quartz and Mn(OH) 2(s): γ sn = 262–272 mJ/m 2. As a result, this study provides new qualitative and quantitative information about heterogeneous nucleation on environmentally an abundant mineral surface, quartz, and it offers important underpinnings for understanding the fate and transport of trace ions in environmental systems.« less

The role of film interfaces in near-ultraviolet absorption and pulsed-laser damage in ion-beam-sputtered coatings based on HfO 2/SiO 2 thin-film pairs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ristau, Detlev; Papernov, S.; Kozlov, A. A.

2015-11-23

The role of thin-film interfaces in the near-ultraviolet absorption and pulsed-laser–induced damage was studied for ion-beam–sputtered and electron-beam–evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage-threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and an E-field peak and averagemore » intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces, as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-ultraviolet, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. Here, the results are explained through the similarity of interfacial film structure with structure formed during the co-deposition of HfO 2 and SiO 2 materials.« less

Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles.

PubMed

Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

2015-11-02

Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials.

Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles

PubMed Central

Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

2015-01-01

Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials. PMID:26522701

Garnet Electrolyte with an Ultralow Interfacial Resistance for Li-Metal Batteries.

PubMed

Li, Yutao; Chen, Xi; Dolocan, Andrei; Cui, Zhiming; Xin, Sen; Xue, Leigang; Xu, Henghui; Park, Kyusung; Goodenough, John B

2018-05-23

Garnet-structured Li 7 La 3 Zr 2 O 12 is a promising solid Li-ion electrolyte for all-solid-state Li-metal batteries and Li-redox-flow batteries owing to its high Li-ion conductivity at room temperature and good electrochemical stability with Li metal. However, there are still three major challenges unsolved: (1) the controversial electrochemical window of garnet, (2) the impractically large resistance at a garnet/electrode interface and the fast lithium-dendrite growth along the grain boundaries of the garnet pellet, and (3) the fast degradation during storage. We have found that these challenges are closely related to a thick Li 2 CO 3 layer and the Li-Al-O glass phase on the surface of garnet materials. Here we introduce a simple method to remove Li 2 CO 3 and the protons in the garnet framework by reacting garnet with carbon at 700 °C; moreover, the amount of the Li-Al-O glass phase with a low Li-ion conductivity in the grain boundary on the garnet surface was also reduced. The surface of the carbon-treated garnet pellets is free of Li 2 CO 3 and is wet by a metallic lithium anode, an organic electrolyte, and a solid composite cathode. The carbon post-treatment has reduced significantly the interfacial resistances to 28, 92 (at 65 °C), and 45 Ω cm 2 at Li/garnet, garnet/LiFePO 4 , and garnet/organic-liquid interfaces, respectively. A symmetric Li/garnet/Li, an all-solid-state Li/garnet/LiFePO 4 , and a hybrid Li-S cell show small overpotentials, high Coulombic efficiencies, and stable cycling performance.

Quasichemical analysis of the cluster-pair approximation for the thermodynamics of proton hydration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pollard, Travis; Beck, Thomas L.; Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221

2014-06-14

A theoretical analysis of the cluster-pair approximation (CPA) is presented based on the quasichemical theory of solutions. The sought single-ion hydration free energy of the proton includes an interfacial potential contribution by definition. It is shown, however, that the CPA involves an extra-thermodynamic assumption that does not guarantee uniform convergence to a bulk free energy value with increasing cluster size. A numerical test of the CPA is performed using the classical polarizable AMOEBA force field and supporting quantum chemical calculations. The enthalpy and free energy differences are computed for the kosmotropic Na{sup +}/F{sup −} ion pair in water clusters ofmore » size n = 5, 25, 105. Additional calculations are performed for the chaotropic Rb{sup +}/I{sup −} ion pair. A small shift in the proton hydration free energy and a larger shift in the hydration enthalpy, relative to the CPA values, are predicted based on the n = 105 simulations. The shifts arise from a combination of sequential hydration and interfacial potential effects. The AMOEBA and quantum chemical results suggest an electrochemical surface potential of water in the range −0.4 to −0.5 V. The physical content of single-ion free energies and implications for ion-water force field development are also discussed.« less

Seamless growth of a supramolecular carpet

PubMed Central

Kim, Ju-Hyung; Ribierre, Jean-Charles; Yang, Yu Seok; Adachi, Chihaya; Kawai, Maki; Jung, Jaehoon; Fukushima, Takanori; Kim, Yousoo

2016-01-01

Organic/metal interfaces play crucial roles in the formation of intermolecular networks on metal surfaces and the performance of organic devices. Although their purity and uniformity have profound effects on the operation of organic devices, the formation of organic thin films with high interfacial uniformity on metal surfaces has suffered from the intrinsic limitation of molecular ordering imposed by irregular surface structures. Here we demonstrate a supramolecular carpet with widely uniform interfacial structure and high adaptability on a metal surface via a one-step process. The high uniformity is achieved with well-balanced interfacial interactions and site-specific molecular rearrangements, even on a pre-annealed amorphous gold surface. Co-existing electronic structures show selective availability corresponding to the energy region and the local position of the system. These findings provide not only a deeper insight into organic thin films with high structural integrity, but also a new way to tailor interfacial geometric and electronic structures. PMID:26839053

Interplay between Interfacial Structures and Device Performance in Organic Solar Cells: A Case Study with the Low Work Function Metal, Calcium.

PubMed

Ju, Huanxin; Knesting, Kristina M; Zhang, Wei; Pan, Xiao; Wang, Chia-Hsin; Yang, Yaw-Wen; Ginger, David S; Zhu, Junfa

2016-01-27

A better understanding of how interfacial structure affects charge carrier recombination would benefit the development of highly efficient organic photovoltaic (OPV) devices. In this paper, transient photovoltage (TPV) and charge extraction (CE) measurements are used in combination with synchrotron radiation photoemission spectroscopy (SRPES) to gain insight into the correlation between interfacial properties and device performance. OPV devices based on PCDTBT/PC71BM with a Ca interlayer were studied as a reference system to investigate the interfacial effects on device performance. Devices with a Ca interlayer exhibit a lower recombination than devices with only an Al cathode at a given charge carrier density (n). In addition, the interfacial band structures indicate that the strong dipole moment produced by the Ca interlayer can facilitate the extraction of electrons and drive holes away from the cathode/polymer interface, resulting in beneficial reduction in interfacial recombination losses. These results help explain the higher efficiencies of devices made with Ca interlayers compared to that without the Ca interlayer.

Accurate determination of interfacial protein secondary structure by combining interfacial-sensitive amide I and amide III spectral signals.

PubMed

Ye, Shuji; Li, Hongchun; Yang, Weilai; Luo, Yi

2014-01-29

Accurate determination of protein structures at the interface is essential to understand the nature of interfacial protein interactions, but it can only be done with a few, very limited experimental methods. Here, we demonstrate for the first time that sum frequency generation vibrational spectroscopy can unambiguously differentiate the interfacial protein secondary structures by combining surface-sensitive amide I and amide III spectral signals. This combination offers a powerful tool to directly distinguish random-coil (disordered) and α-helical structures in proteins. From a systematic study on the interactions between several antimicrobial peptides (including LKα14, mastoparan X, cecropin P1, melittin, and pardaxin) and lipid bilayers, it is found that the spectral profiles of the random-coil and α-helical structures are well separated in the amide III spectra, appearing below and above 1260 cm(-1), respectively. For the peptides with a straight backbone chain, the strength ratio for the peaks of the random-coil and α-helical structures shows a distinct linear relationship with the fraction of the disordered structure deduced from independent NMR experiments reported in the literature. It is revealed that increasing the fraction of negatively charged lipids can induce a conformational change of pardaxin from random-coil to α-helical structures. This experimental protocol can be employed for determining the interfacial protein secondary structures and dynamics in situ and in real time without extraneous labels.

Interfacial patterns in magnetorheological fluids: Azimuthal field-induced structures.

PubMed

Dias, Eduardo O; Lira, Sérgio A; Miranda, José A

2015-08-01

Despite their practical and academic relevance, studies of interfacial pattern formation in confined magnetorheological (MR) fluids have been largely overlooked in the literature. In this work, we present a contribution to this soft matter research topic and investigate the emergence of interfacial instabilities when an inviscid, initially circular bubble of a Newtonian fluid is surrounded by a MR fluid in a Hele-Shaw cell apparatus. An externally applied, in-plane azimuthal magnetic field produced by a current-carrying wire induces interfacial disturbances at the two-fluid interface, and pattern-forming structures arise. Linear stability analysis, weakly nonlinear theory, and a vortex sheet approach are used to access early linear and intermediate nonlinear time regimes, as well as to determine stationary interfacial shapes at fully nonlinear stages.

Multimodal Characterization of the Morphology and Functional Interfaces in Composite Electrodes for Li-S Batteries by Li Ion and Electron Beams.

PubMed

Oleshko, Vladimir P; Herzing, Andrew A; Twedt, Kevin A; Griebel, Jared J; McClelland, Jabez J; Pyun, Jeffrey; Soles, Christopher L

2017-09-19

We report the characterization of multiscale 3D structural architectures of novel poly[sulfur-random-(1,3-diisopropenylbenzene)] copolymer-based cathodes for high-energy-density Li-S batteries capable of realizing discharge capacities >1000 mAh/g and long cycling lifetimes >500 cycles. Hierarchical morphologies and interfacial structures have been investigated by a combination of focused Li ion beam (LiFIB) and analytical electron microscopy in relation to the electrochemical performance and physicomechanical stability of the cathodes. Charge-free surface topography and composition-sensitive imaging of the electrodes was performed using recently introduced low-energy scanning LiFIB with Li + probe sizes of a few tens of nanometers at 5 keV energy and 1 pA probe current. Furthermore, we demonstrate that LiFIB has the ability to inject a certain number of Li cations into the material with nanoscale precision, potentially enabling control of the state of discharge in the selected area. We show that chemical modification of the cathodes by replacing the elemental sulfur with organosulfur copolymers significantly improves its structural integrity and compositional homogeneity down to the sub-5-nm length scale, resulting in the creation of (a) robust functional interfaces and percolated conductive pathways involving graphitic-like outer shells of aggregated nanocarbons and (b) extended micro- and mesoscale porosities required for effective ion transport.

Revealing the Self-Degradation Mechanisms in Methylammonium Lead Iodide Perovskites in Dark and Vacuum.

PubMed

Gunasekaran, Rajendra Kumar; Chinnadurai, Deviprasath; Selvaraj, Aravindha Raja; Rajendiran, Rajmohan; Senthil, Karuppanan; Prabakar, Kandasamy

2018-06-19

Organic-inorganic lead halide perovskite phases segregate (and their structures degrade) under illumination, exhibiting a poor stability with hysteresis and producing halide accumulation at the surface.In this work, we observed structural and interfacial dissociation in methylammonium lead iodide (CH 3 NH 3 PbI 3 ) perovskites even under dark and vacuum conditions. Here, we investigate the origin and consequences of self-degradation in CH 3 NH 3 PbI 3 perovskites stored in the dark under vacuum. Diffraction and photoelectron spectroscopic studies reveal the structural dissociation of perovskites into PbI 2 , which further dissociates into metallic lead (Pb 0 ) and I 2 - ions, collectively degrading the perovskite stability. Using TOF-SIMS analysis, AuI 2 - formation was directly observed, and it was found that an interplay between CH 3 NH 3 + , I 3 - , and mobile I - ions continuously regenerates more I 2 - ions, which diffuse to the surface even in the absence of light. Besides, halide diffusion causes a concentration gradient between Pb 0 and I 2 - and creates other ionic traps (PbI 2 - , PbI - ) that segregate as clusters at the perovskite/gold interface. A shift of the onset of the absorption band edge towards shorter wavelengths was also observed by absorption spectroscopy, indicating the formation of defect species upon aging in the dark under vacuum. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interfacial binding of divalent cations to calixarene-based Langmuir monolayers

DOE PAGES

Tulli, Ludovico G.; Wang, Wenjie; Lindemann, William R.; ...

2015-02-20

The interactions of Langmuir monolayers produced through the self-assembly of an amphiphilic p-carboxycalix[4]arene with a series of divalent, fourth-period transition metals, at the air-water interface, were investigated. Changes in the interfacial behavior of 1 in response to the presence of CuCl 2, CoCl 2, MnCl 2, and NiCl 2 were studied by means of Langmuir compression isotherms and Brewster angle microscopy (BAM). The measurements revealed that the self-assembly properties of 1 are significantly affected by Cu 2+ ions. The interactions of 1-based monolayers with Co 2+ and Cu 2+ ions were further investigated by means of synchrotron radiation-based X-ray reflectivitymore » (XRR), X-ray near-total-reflection fluorescence (XNTRF), and grazing incidence X-ray diffraction (GIXD). XNTRF and XRR analyses revealed that the monolayer of 1 binds more strongly to Cu 2+ than Co 2+ ions. In the presence of relatively high concentrations of Cu 2+ ions in the subphase (1.4 × 10 -3 M), XNTRF exhibited anomalous depth profile behavior and GIXD measurements showed considerably strong diffuse scattering. Furthermore, both measurements suggest the formation of Cu 2+ clusters contiguous to the monolayer of 1.« less

Fundamental tribological properties of ion-beam-deposited boron nitride films

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1989-01-01

The adhesion, friction, and micromechanical properties of ion-beam-deposited boron nitride (BN) films are reviewed. The BN films are examined in contact with BN metals and other harder materials. For simplicity of discussion, the tribological properties of concern in the processes are separated into two parts. First, the pull-off force (adhesion) and the shear force required to break the interfacial junctions between contacting surfaces are discussed. The effects of surface films, hardness of metals, and temperature on tribological response with respect to adhesion and friction are considered. The second part deals with the abrasion of the BN films. Elastic, plastic, and fracture behavior of the BN films in solid-state contact are discussed. The scratch technique of determining the critical load needed to fracture interfacial adhesive bonds of BN films deposited on substrates is also addressed.

Fundamental tribological properties of ion-beam-deposited boron nitride films

NASA Technical Reports Server (NTRS)

Miyoshi, K.

1990-01-01

The adhesion, friction, and micromechanical properties of ion-beam-deposited boron nitride (BN) films are reviewed. The BN films are examined in contact with BN metals and other harder materials. For simplicity of discussion, the tribological properties of concern in the processes are separated into two parts. First, the pull-off force (adhesion) and the shear force required to break the interfacial junctions between contacting surfaces are discussed. The effects of surface films, hardness of metals, and temperature on tribological response with respect to adhesion and friction are considered. The second part deals with the abrasion of the BN films. Elastic, plastic, and fracture behavior of the BN films in solid-state contact are discussed. The scratch technique of determining the critical load needed to fracture interfacial adhesive bonds of BN films deposited on substrates is also addressed.

Enhancement of the Device Performance and the Stability with a Homojunction-structured Tungsten Indium Zinc Oxide Thin Film Transistor.

PubMed

Park, Hyun-Woo; Song, Aeran; Choi, Dukhyun; Kim, Hyung-Jun; Kwon, Jang-Yeon; Chung, Kwun-Bum

2017-09-14

Tungsten-indium-zinc-oxide thin-film transistors (WIZO-TFTs) were fabricated using a radio frequency (RF) co-sputtering system with two types of source/drain (S/D)-electrode material of conducting WIZO (homojunction structure) and the indium-tin oxide (ITO) (heterojunction structure) on the same WIZO active-channel layer. The electrical properties of the WIZO layers used in the S/D electrode and the active-channel layer were adjusted through oxygen partial pressure during the deposition process. To explain enhancements of the device performance and stability of the homojunction-structured WIZO-TFT, a systematic investigation of correlation between device performance and physical properties at the interface between the active layer and the S/D electrodes such as the contact resistance, surface/interfacial roughness, interfacial-trap density, and interfacial energy-level alignments was conducted. The homojunction-structured WIZO-TFT exhibited a lower contact resistance, smaller interfacial-trap density, and flatter interfacial roughness than the WIZO-TFT with the heterojunction structure. The 0.09 eV electron barrier of the homojunction-structured WIZO-TFT is lower than the 0.21 eV value that was obtained for the heterojunction-structured WIZO-TFT. This reduced electron barrier may be attributed to enhancements of device performance and stability, that are related to the carrier transport.

Investigation of thermal energy transport interface of hybrid graphene-carbon nanotube/polyethylene nanocomposites.

PubMed

Liu, Feng; Liu, Xuyang; Hu, Ning; Ning, Huiming; Atobe, Satoshi; Yan, Cheng; Mo, Fuhao; Fu, Shaoyun; Zhang, Jianyu; Wang, Yu; Mu, Xiaojing

2017-10-31

It is well known the thermal properties of three-dimensional (3-D) hybrid graphene (GR)-carbon nanotube (CNT) structures are not superior to that of the individual GR and CNT, however, the 3-D hybrid GR-CNT structures can effectively improve the thermal properties of polymer matrix. Therefore, understanding the thermal energy transport in the interface between polymer matrix and 3-D hybrid GR-CNT structure is essential. Here, the enhancement mechanism of interfacial thermal transport of hybrid GR-CNT structure was explored by applying non-equilibrium molecular dynamics (NEMD) simulations. Three different types of hybrid GR-CNT structures were built. The influences of CNT radius and CNT type for the hybrid GR-CNT on the interfacial thermal properties were also analyzed. Computational results show that among the three different types of hybrid GR-CNT structures, the Model-I, i.e., the covalent bond hybrid GR-CNT structures are of the best interfacial thermal properties. Meanwhile, the CNT radius of hybrid GR-CNT structure has a great influence on the interfacial thermal properties.

Monolithic All-Phosphate Solid-State Lithium-Ion Battery with Improved Interfacial Compatibility.

PubMed

Yu, Shicheng; Mertens, Andreas; Tempel, Hermann; Schierholz, Roland; Kungl, Hans; Eichel, Rüdiger-A

2018-06-22

High interfacial resistance between solid electrolyte and electrode of ceramic all-solid-state batteries is a major reason for the reduced performance of these batteries. A solid-state battery using a monolithic all-phosphate concept based on screen printed thick LiTi 2 (PO 4 ) 3 anode and Li 3 V 2 (PO 4 ) 3 cathode composite layers on a densely sintered Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 solid electrolyte has been realized with competitive cycling performance. The choice of materials was primarily based on the (electro-)chemical and mechanical matching of the components instead of solely focusing on high-performance of individual components. Thus, the battery utilized a phosphate backbone in combination with tailored morphology of the electrode materials to ensure good interfacial matching for a durable mechanical stability. Moreover, the operating voltage range of the active materials matches with the intrinsic electrochemical window of the electrolyte which resulted in high electrochemical stability. A highly competitive discharge capacity of 63.5 mAh g -1 at 0.39 C after 500 cycles, corresponding to 84% of the initial discharge capacity, was achieved. The analysis of interfacial charge transfer kinetics confirmed the structural and electrical properties of the electrodes and their interfaces with the electrolyte, as evidenced by the excellent cycling performance of the all-phosphate solid-state battery. These interfaces have been studied via impedance analysis with subsequent distribution of relaxation times analysis. Moreover, the prepared solid-state battery could be processed and operated in air atmosphere owing to the low oxygen sensitivity of the phosphate materials. The analysis of electrolyte/electrode interfaces after cycling demonstrates that the interfaces remained stable during cycling.

A photofunctional bottom-up bis(dipyrrinato)zinc(II) complex nanosheet

PubMed Central

Sakamoto, Ryota; Hoshiko, Ken; Liu, Qian; Yagi, Toshiki; Nagayama, Tatsuhiro; Kusaka, Shinpei; Tsuchiya, Mizuho; Kitagawa, Yasutaka; Wong, Wai-Yeung; Nishihara, Hiroshi

2015-01-01

Two-dimensional polymeric nanosheets have recently gained much attention, particularly top-down nanosheets such as graphene and metal chalcogenides originating from bulk-layered mother materials. Although molecule-based bottom-up nanosheets manufactured directly from molecular components can exhibit greater structural diversity than top-down nanosheets, the bottom-up nanosheets reported thus far lack useful functionalities. Here we show the design and synthesis of a bottom-up nanosheet featuring a photoactive bis(dipyrrinato)zinc(II) complex motif. A liquid/liquid interfacial synthesis between a three-way dipyrrin ligand and zinc(II) ions results in a multi-layer nanosheet, whereas an air/liquid interfacial reaction produces a single-layer or few-layer nanosheet with domain sizes of >10 μm on one side. The bis(dipyrrinato)zinc(II) metal complex nanosheet is easy to deposit on various substrates using the Langmuir–Schäfer process. The nanosheet deposited on a transparent SnO2 electrode functions as a photoanode in a photoelectric conversion system, and is thus the first photofunctional bottom-up nanosheet. PMID:25831973

Schottky barrier and band edge engineering via the interfacial structure and strain for the Pt/TiO2 heterostructure.

PubMed

Ma, Xiangchao; Wu, Xin; Wang, Yucheng; Dai, Ying

2017-07-19

Charge transfer across the Pt/TiO 2 interface, which is mainly determined by the interface Schottky barrier height (SBH), is an important process in the (photo)catalytic and electronic applications of the Pt/TiO 2 composite. Therefore, systematic investigation of the factors that affect the interface SBH is indispensable for understanding and optimizing its performance. In this work, a systematic study of the effects of the interfacial structure and strain on the SBH of the Pt/TiO 2 (001) interface has been carried out based on the first-principles calculations. The results of interface adhesion energy show that two different interfacial structures for the Pt/TiO 2 (001) heterointerface may exist experimentally, namely, O-Pt bonding and Ti-Pt bonding. Moreover, the interfacial structures result in not only different values for the SBH, but also different dependences of the SBH on strain. Detailed investigations show that these versatile modulations of the SBH with the structure and strain are mainly attributed to the strong dependence of the band edges of TiO 2 and the interfacial potential alignments on the strain and structure, suggesting that these results are general and may be applicable to other metal/TiO 2 heterostructures.

Effects of Alternating Hydrogenated and Protonated Segments in polymers on their Wettability.

NASA Astrophysics Data System (ADS)

Smith, Dennis; Traiphol, Rakchart; Cheng, Gang; Perahia, Dvora

2003-03-01

Polymers consisting of alternating hydrogenated and fluorinated segments exhibit unique interfacial characteristics governed by the components that dominate the interface. Presence of fluorine reduces the interfacial energy and is expected to decrease the adhesion to the polymer surface. Thin liquid crystalline (LC) layers of 4,4?-octyl-cyanobiphenyl, cast on top of a polymeric layer consisting of alternating methylstylbine protonated segments bridged by a fluorinated group was used as a mechanistic tool to study of interfacial effects on three parameters: wetting, interfacial alignment and surface induces structures. The liquid crystal cast on a low interfacial energy fluorinated polymeric film exhibits bulk homeotropic alignment as expected. However it fully wetted the polymer surface despite the incompatibility of the protonated LC and mainly fluorinated polymer interface. Further more, it was found to stabilize the interfacial Semitic layers to a higher temperature and induce different surface ordering that was not observed at the same temperature neither in the bulk nor at the interfaces with silicon or glass surface. These results indicate that the interfacial interactions of polymers with liquid crystals are a complex function of both surface energies and the interfacial structure of the polymer.

Homogeneously dispersed CeO2 nanoparticles on exfoliated hexaniobate nanosheets

NASA Astrophysics Data System (ADS)

Marques, Thalles M. F.; Strayer, Megan E.; Ghosh, Anupama; Silva, Alexandre; Ferreira, Odair P.; Fujisawa, Kazunori; Alves da Cunha, Jose R.; Abreu, Guilherme J. P.; Terrones, Mauricio; Mallouk, Thomas E.; Viana, Bartolomeu C.

2017-12-01

Hexaniobate nanosheets derived from the parent compound K4Nb6O17 have been decorated with CeO2 nanoparticles by ion exchange with aqueous cerium (IV) solution. Very homogeneous CeO2 nanoparticle decoration of the hexaniobate sheets can be achieved by this method and the resulting composites may absorb visible light. HRTEM images show that ∼3.0 nm diameter CeO2 nanoparticles adhere to hexaniobate nanosheets that are exfoliated and then restacked prior to Ce deposition. The interfacial interaction between CeO2 nanoparticles and nanosheets would be due to an electrostatic attraction mechanism. Raman and XRD measurements have given strong evidence that CeO2 nanoparticles have fluorite structure. EDS, FTIR and XPS results suggest almost complete exchange of TBA+ and K+ by Ce4+. Cerium ion exchange on the acid exchanged parent compound, H2.9K1.1Nb6O17, revealed that the extent of Ce ion exchange is much greater in case of nanosheets, which may be rationalized by the larger surface area available after exfoliation. XPS measurements show that the ratio of Ce4+/Ce3+ is around 4.4, in agreement with the formation of fluorite structure (CeO2). Thus, these CeO2 nanoparticle/nanosheet composites may be useful for catalytic processes.

Swift heavy ion irradiation effects on structural, optical properties and ac conductivity of polypyrrole nanofibers

NASA Astrophysics Data System (ADS)

Hazarika, J.; Kumar, A.

2016-12-01

Polypyrrole (PPy) nanofibers have been synthesized by interfacial polymerization method and irradiated with 160 MeV Ni12+ ions under vacuum with fluences in the range of 1010-1012 ions/cm2. High-resolution transmission electron microscopy results show that upon swift heavy ion (SHI) irradiation the PPy nanofibers become denser. The crystallinity of PPy nanofibers increases upon SHI irradiation, while their d-spacing decreases. Upon SHI irradiation, the polaron absorption band gets red-shifted indicating reduction in the optical band gap energy of the irradiated PPy nanofibers. The indirect optical band gap energy is decreased as compared to corresponding direct optical band gap energy. The number of carbon atoms per conjugation length (N) and carbon atoms per cluster (M) of the SHI-irradiated PPy nanofibers increase with increasing the irradiation fluence. Fourier transform infrared spectra reveal the enhancement in intensity of some characteristic vibration bands upon SHI irradiation. The thermal stability of the PPy nanofibers is enhanced on SHI irradiation. The charge carriers in both pristine and irradiated PPy nanofibers follow the correlated barrier hopping mechanism. Scaling of ac conductivity reveals that the conduction mechanism is independent of the SHI irradiation fluence.

Two-Fluid Models and Interfacial Area Transport in Microgravity Condition

NASA Technical Reports Server (NTRS)

Ishii, Mamoru; Sun, Xiao-Dong; Vasavada, Shilp

2004-01-01

The objective of the present study is to develop a two-fluid model formulation with interfacial area transport equation applicable for microgravity conditions. The new model is expected to make a leapfrog improvement by furnishing the constitutive relations for the interfacial interaction terms with the interfacial area transport equation, which can dynamically model the changes of the interfacial structures. In the first year of this three-year project supported by the U.S. NASA, Office of Biological and Physics Research, the primary focus is to design and construct a ground-based, microgravity two-phase flow simulation facility, in which two immiscible fluids with close density will be used. In predicting the two-phase flow behaviors in any two-phase flow system, the interfacial transfer terms are among the most essential factors in the modeling. These interfacial transfer terms in a two-fluid model specify the rate of phase change, momentum exchange, and energy transfer at the interface between the two phases. For the two-phase flow under the microgravity condition, the stability of the fluid particle interface and the interfacial structures are quite different from those under normal gravity condition. The flow structure may not reach an equilibrium condition and the two fluids may be loosely coupled such that the inertia terms of each fluid should be considered separately by use of the two-fluid model. Previous studies indicated that, unless phase-interaction terms are accurately modeled in the two-fluid model, the complex modeling does not necessarily warrant an accurate solution.

Present understanding of the stability of Li-stuffed garnets with moisture, carbon dioxide, and metallic lithium

NASA Astrophysics Data System (ADS)

Hofstetter, Kyle; Samson, Alfred Junio; Narayanan, Sumaletha; Thangadurai, Venkataraman

2018-06-01

Fast lithium-ion conducting garnet-type metal oxides are promising membranes for next-generation all-solid-state Li batteries and beyond Li-ion batteries, including Li-air and Li-S batteries, due to their high total Li-ion conductivity and excellent chemical stability against reaction with elemental Li. Several studies have been reported on structure-chemical composition-ionic conductivity property in Li-stuffed garnet-type metal oxides. Here, an overview of the chemical and electrochemical stability of lithium-based garnets against moisture/humidity, aqueous solutions, carbon dioxide, sulfur, and metallic lithium are analyzed. Moisture and aqueous stability studies focus on understanding the crystal structure stability, the proton exchange capacity as a function of Li content in Li-stuffed garnets, and how the protonated species affect the crystal structure and mass transport properties. H+/Li+ exchange was found to be in the range of 2-100%. Stability concerning Li-ion conductivity and morphology under carbon dioxide are discussed. Interfacial chemical stability with lithium metal characterized by electrochemical stability window, Li dendrite formation and area specific resistance (ASR) for the reaction Li ⇌ Li+ +e- are presented. Recent attempts to suppress dendrite formation and to reduce ASR via surface modification are also highlighted. Li and Li-stuffed garnet interface ASR values are shown to be as high as >2000 Ω cm2 and as low as 1 Ω cm2 at room temperature for surface modified Li-stuffed samples. Furthermore, recent studies on Li-S battery utilizing chemically stable Li - garnet electrolyte are also discussed.

Simulation of Peptides at Aqueous Interfaces

NASA Technical Reports Server (NTRS)

Pohorille, Andrew; Wilson, M.; Chipot, C.; DeVincenzi, Donald L. (Technical Monitor)

2001-01-01

Behavior of peptides at water-membrane interfaces is of great interest in studies on cellular transport and signaling, membrane fusion, and the action of toxins and antibiotics. Many peptides, which exist in water only as random coils, can form sequence-dependent, ordered structures at aqueous interfaces, incorporate into membranes and self-assembly into functional units, such as simple ion channels. Multi -nanosecond molecular dynamics simulations have been carried out to study the mechanism and energetics of interfacial folding of both non-polar and amphiphilic peptides, their insertion into membranes and association into higher-order structures. The simulations indicate that peptides fold non-sequentially, often through a series of amphiphilic intermediates. They further incorporate into the membrane in a preferred direction as folded monomers, and only then aggregate into dimers and, possibly, further into "dimers of dimers".

Cr/B 4C multilayer mirrors: Study of interfaces and X-ray reflectance

DOE PAGES

Burcklen, C.; Soufli, R.; Gullikson, E.; ...

2016-03-24

Here, we present an experimental study of the effect of layer interfaces on the x-ray reflectance in Cr/B 4C multilayer interference coatings with layer thicknesses ranging from 0.7 nm to 5.4 nm. The multilayers were deposited by magnetron sputtering and by ion beam sputtering. Grazing incidence x-ray reflectometry, soft x-ray reflectometry, and transmission electron microscopy reveal asymmetric multilayer structures with a larger B 4C-on-Cr interface, which we modeled with a 1–1.5 nm thick interfacial layer. Reflectance measurements in the vicinity of the Cr L 2,3 absorption edge demonstrate fine structure that is not predicted by simulations using the currently tabulatedmore » refractive index (optical constants) values for Cr.« less

Coupling of order parameters, chirality, and interfacial structures in multiferroic materials.

PubMed

Conti, Sergio; Müller, Stefan; Poliakovsky, Arkady; Salje, Ekhard K H

2011-04-13

We study optimal interfacial structures in multiferroic materials with a biquadratic coupling between two order parameters. We discover a new duality relation between the strong coupling and the weak coupling regime for the case of isotropic gradient terms. We analyze the phase diagram depending on the coupling constant and anisotropy of the gradient term, and show that in a certain regime the secondary order parameter becomes activated only in the interfacial region.

Interfacial assignment of branched-alkyl benzene sulfonates: A molecular simulation

NASA Astrophysics Data System (ADS)

Liu, Zi-Yu; Wei, Ning; Wang, Ce; Zhou, He; Zhang, Lei; Liao, Qi; Zhang, Lu

2015-11-01

A molecular dynamics simulation was conducted to analyze orientations of sodium branched-alkyl benzene sulfonates molecules at nonane/water interface, which is helpful to design optimal surfactant structures to achieve ultralow interfacial tension (IFT). Through the two dimensional density profiles, monolayer collapses are found when surfactant concentration continues to increase. Thus the precise scope of monolayer is certain and orientation can be analyzed. Based on the simulated results, we verdict the interfacial assignment of branched-alkyl benzene sulfonates at the oil-water interface, and discuss the effect of hydrophobic tail structure on surfactant assignment. Bigger hydrophobic size can slow the change rate of surfactant occupied area as steric hindrance, and surfactant meta hydrophobic tails have a stronger tendency to stretch to the oil phase below the collapsed concentration. Furthermore, an interfacial model with reference to collapse, increasing steric hindrance and charge repulsive force between interfacial surfactant molecules, responsible for effecting of surfactant concentration and structure has been supposed.

Ab Initio Study of Interfacial Structure Transformation of Amorphous Carbon Catalyzed by Ti, Cr, and W Transition Layers.

PubMed

Li, Xiaowei; Li, Lei; Zhang, Dong; Wang, Aiying

2017-11-29

Amorphous carbon (a-C) films composited with transition layers exhibit the desirable improvement of adhesion strength between films and substrate, but the further understanding on the interfacial structure transformation of a-C structure induced by transition layers is still lacked. In this paper, using ab initio calculations, we comparatively studied the interfacial structure between Ti, Cr, or W transition layers and a-C film from the atomic scale, and demonstrated that the addition of Ti, Cr, or W catalyzed the graphitic transformation of a-C structure at different levels, which provided the theoretical guidance for designing a multilayer nanocomposite film for renewed application.

Structure and orientation of interfacial proteins determined by sum frequency generation vibrational spectroscopy: method and application.

PubMed

Ye, Shuji; Wei, Feng; Li, Hongchun; Tian, Kangzhen; Luo, Yi

2013-01-01

In situ and real-time characterization of molecular structures and orientation of proteins at interfaces is essential to understand the nature of interfacial protein interaction. Such work will undoubtedly provide important clues to control biointerface in a desired manner. Sum frequency generation vibrational spectroscopy (SFG-VS) has been demonstrated to be a powerful technique to study the interfacial structures and interactions at the molecular level. This paper first systematically introduced the methods for the calculation of the Raman polarizability tensor, infrared transition dipole moment, and SFG molecular hyperpolarizability tensor elements of proteins/peptides with the secondary structures of α-helix, 310-helix, antiparallel β-sheet, and parallel β-sheet, as well as the methodology to determine the orientation of interfacial protein secondary structures using SFG amide I spectra. After that, recent progresses on the determination of protein structure and orientation at different interfaces by SFG-VS were then reviewed, which provides a molecular-level understanding of the structures and interactions of interfacial proteins, specially understanding the nature of driving force behind such interactions. Although this review has focused on analysis of amide I spectra, it will be expected to offer a basic idea for the spectral analysis of amide III SFG signals and other complicated molecular systems such as RNA and DNA. Copyright © 2013 Elsevier Inc. All rights reserved.

Studying protein structural changes based on surface plasmon resonance and surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Hu, Wen-Pin; Chen, Shean-Jen; Yih, Jenq-Nan; Lin, G.-Y.; Chang, Guan L.

2004-06-01

The ability to recognize the conformational changes and structural variations of a protein when immobilized in a solid surface is of great importance in a variety of applications. Surface plasmon resonance (SPR) sensing is an appropriate technique for investigating interfacial phenomena, and enables the conformational changes of proteins to be monitored through the variation in the SPR angle shift. Meanwhile, the surface-enhanced Raman scattering (SERS) system can also assist in clarifying the changes in protein structure. The present study utilizes a 1 mM CrO3 phosphate buffer solution (PBS) to induce conformational changes of human serum albumin (HSA). Monitoring the corresponding SPR angle shifts and the SPR reflectivity spectrum enables the relationships between the conformational changes of the surface-immobilized protein and the thickness and dielectric constants of the protein layer to be estimated. The experimental SPR results indicate that the Cr6+ ions cause significant conformational change of the protein. It is established that the ions are not merely absorbed into the protein as a result of electrostatic forces, but that complex protein refolding events also take place. Furthermore, the data acquired from the SERS system yield valuable information regarding the changes which take place in the protein structure.

Effects of cathode electrolyte interfacial (CEI) layer on long term cycling of all-solid-state thin-film batteries

DOE PAGES

Wang, Ziying; Lee, Jungwoo Z.; Xin, Huolin L.; ...

2016-05-30

All-solid-state lithium-ion batteries have the potential to not only push the current limits of energy density by utilizing Li metal, but also improve safety by avoiding flammable organic electrolyte. However, understanding the role of solid electrolyte – electrode interfaces will be critical to improve performance. In this paper, we conducted long term cycling on commercially available lithium cobalt oxide (LCO)/lithium phosphorus oxynitride (LiPON)/lithium (Li) cells at elevated temperature to investigate the interfacial phenomena that lead to capacity decay. STEM-EELS analysis of samples revealed a previously unreported disordered layer between the LCO cathode and LiPON electrolyte. This electrochemically inactive layer grewmore » in thickness leading to loss of capacity and increase of interfacial resistance when cycled at 80 °C. Finally, the stabilization of this layer through interfacial engineering is crucial to improve the long term performance of thin-film batteries especially under thermal stress.« less

Development of w/o microemulsion for transdermal delivery of iodide ions.

PubMed

Lou, Hao; Qiu, Ni; Crill, Catherine; Helms, Richard; Almoazen, Hassan

2013-03-01

The objective of this study was to develop a water-in-oil (w/o) microemulsion which can be utilized as a transdermal delivery for iodide ions. Several w/o microemulsion formulations were prepared utilizing Span 20, ethanol, Capryol 90®, and water. The selected formulations had 5%, 10%, 15%, 20%, and a maximum of 23% w/w water content. Potassium iodide (KI) was incorporated in all formulations at 5% w/v. Physicochemical characterizations were conducted to evaluate the structure and stability. These studies included: mean droplet size, pH, viscosity, conductivity, and chemical stability tests. In vitro human skin permeation studies were conducted to evaluate the diffusion of the iodide ion through human skin. The w/o microemulsion formulations were stable and compatible with iodide ions with water content ranging from 5% to 23% w/w. The addition of KI influenced the physicochemical properties of microemulsion as compared to blank microemulsion formulations. In vitro human skin permeation studies indicated that selected formulations improved iodide ion diffusion significantly as compared to control (KI solution; P value<0.05). Iodide ions were entrapped within the aqueous core of w/o microemulsion. Span 20, ethanol and Capryol 90 protected the iodide ions against oxidation and formed a stable microemulsion. It is worth to note that according to Hofmeister series, iodide ions tend to lower the interfacial tension between water and oil and consequently enhance overall stability. This work illustrates that microemulsion system can be utilized as a vehicle for the transdermal administration of iodide.

The hydration structure at yttria-stabilized cubic zirconia (110)-water interface with sub-Ångström resolution

DOE PAGES

Hou, Binyang; Kim, Seunghyun; Kim, Taeho; ...

2016-06-15

The interfacial hydration structure of yttria-stabilized cubic zirconia (110) surface in contact with water was determined with ~0.5 Å resolution by high-resolution X-ray reflectivity measurement. The terminal layer shows a reduced electron density compared to the following substrate lattice layers, which indicates there are additional defects generated by metal depletion as well as intrinsic oxygen vacancies, both of which are apparently filled by water species. Above this top surface layer, two additional adsorbed layers are observed forming a characteristic interfacial hydration structure. The first adsorbed layer shows abnormally high density as pure water and likely includes metal species, whereas themore » second layer consists of pure water. The observed interfacial hydration structure seems responsible for local equilibration of the defective surface in water and eventually regulating the long-term degradation processes. As a result, the multitude of water interactions with the zirconia surface results in the complex but highly ordered interfacial structure constituting the reaction front.« less

Ion Transport in Confined Geometries below the Nanoscale: Access Resistance Dominates Protein Channel Conductance in Diluted Solutions.

PubMed

Alcaraz, Antonio; López, M Lidón; Queralt-Martín, María; Aguilella, Vicente M

2017-10-24

Synthetic nanopores and mesoscopic protein channels have common traits like the importance of electrostatic interactions between the permeating ions and the nanochannel. Ion transport at the nanoscale occurs under confinement conditions so that the usual assumptions made in microfluidics are challenged, among others, by interfacial effects such as access resistance (AR). Here, we show that a sound interpretation of electrophysiological measurements in terms of channel ion selective properties requires the consideration of interfacial effects, up to the point that they dominate protein channel conductance in diluted solutions. We measure AR in a large ion channel, the bacterial porin OmpF, by means of single-channel conductance measurements in electrolyte solutions containing varying concentrations of high molecular weight PEG, sterically excluded from the pore. Comparison of experiments performed in charged and neutral planar membranes shows that lipid surface charges modify the ion distribution and determine the value of AR, indicating that lipid molecules are more than passive scaffolds even in the case of large transmembrane proteins. We also found that AR may reach up to 80% of the total channel conductance in diluted solutions, where electrophysiological recordings register essentially the AR of the system and depend marginally on the pore characteristics. These findings may have implications for several low aspect ratio biological channels that perform their physiological function in a low ionic strength and macromolecule crowded environment, just the two conditions enhancing the AR contribution.

Recovery of cesium

DOEpatents

Izatt, Reed M.; Christensen, James J.; Hawkins, Richard T.

1984-01-01

A process of recovering cesium ions from mixtures of ions containing them and other ions, e.g., a solution of nuclear waste materials, which comprises establishing a separate source phase containing such a mixture of ions, establishing a separate recipient phase, establishing a liquid membrane phase in interfacial contact with said source and recipient phases, said membrane phase containing a ligand, preferably a selected calixarene as depicted in the drawing, maintaining said interfacial contact for a period of time long enough to transport by said ligand a substantial portion of the cesium ion from the source phase to the recipient phase, and recovering the cesium ion from the recipient phase. The separation of the source and recipient phases may be by the membrane phase only, e.g., where these aqueous phases are emulsified as dispersed phases in a continuous membrane phase, or may include a physical barrier as well, e.g., an open-top outer container with an inner open-ended container of smaller cross-section mounted in the outer container with its open bottom end spaced from and above the closed bottom of the outer container so that the membrane phase may fill the outer container to a level above the bottom of the inner container and have floating on its upper surface a source phase and a recipient phase separated by the wall of the inner container as a physical barrier. A preferred solvent for the ligand is a mixture of methylene chloride and carbon tetrachloride.

Research on the interfacial behaviors of plate-type dispersion nuclear fuel elements

NASA Astrophysics Data System (ADS)

Wang, Qiming; Yan, Xiaoqing; Ding, Shurong; Huo, Yongzhong

2010-04-01

The three-dimensional constitutive relations are constructed, respectively, for the fuel particles, the metal matrix and the cladding of dispersion nuclear fuel elements, allowing for the effects of large deformation and thermal-elastoplasticity. According to the constitutive relations, the method of modeling their irradiation behaviors in ABAQUS is developed and validated. Numerical simulations of the interfacial performances between the fuel meat and the cladding are implemented with the developed finite element models for different micro-structures of the fuel meat. The research results indicate that: (1) the interfacial tensile stresses and shear stresses for some cases will increase with burnup, but the relative stresses will decrease with burnup for some micro-structures; (2) at the lower burnups, the interfacial stresses increase with the particle sizes and the particle volume fractions; however, it is not the case at the higher burnups; (3) the particle distribution characteristics distinctly affect the interfacial stresses, and the face-centered cubic case has the best interfacial performance of the three considered cases.

Interfacial nanodroplets guided construction of hierarchical Au, Au-Pt, and Au-Pd particles as excellent catalysts

NASA Astrophysics Data System (ADS)

Ma, Aijing; Xu, Jie; Zhang, Xuehua; Zhang, Bin; Wang, Dayang; Xu, Haolan

2014-05-01

Interfacial nanodroplets were grafted to the surfaces of self-sacrificed template particles in a galvanic reaction system to assist the construction of 3D Au porous structures. The interfacial nanodroplets were formed via direct adsorption of surfactant-free emulsions onto the particle surfaces. The interfacial nanodroplets discretely distributed at the template particle surfaces and served as soft templates to guide the formation of porous Au structures. The self-variation of footprint sizes of interfacial nanodroplets during Au growth gave rise to a hierarchical pore size distribution of the obtained Au porous particles. This strategy could be easily extended to synthesize bimetal porous particles such as Au-Pt and Au-Pd. The obtained porous Au, Au-Pt, and Au-Pd particles showed excellent catalytic activity in catalytic reduction of 4-nitrophenol.

Structural and Electrochemical Consequences of Al and Ga Cosubstitution in Li7La3Zr2O12 Solid Electrolytes

PubMed Central

2016-01-01

Several “Beyond Li-Ion Battery” concepts such as all solid-state batteries and hybrid liquid/solid systems envision the use of a solid electrolyte to protect Li-metal anodes. These configurations are very attractive due to the possibility of exceptionally high energy densities and high (dis)charge rates, but they are far from being realized practically due to a number of issues including high interfacial resistance and difficulties associated with fabrication. One of the most promising solid electrolyte systems for these applications is Al or Ga stabilized Li7La3Zr2O12 (LLZO) based on high ionic conductivities and apparent stability against reduction by Li metal. Nevertheless, the fabrication of dense LLZO membranes with high ionic conductivity and low interfacial resistances remains challenging; it definitely requires a better understanding of the structural and electrochemical properties. In this study, the phase transition from garnet (Ia3̅d, No. 230) to “non-garnet” (I4̅3d, No. 220) space group as a function of composition and the different sintering behavior of Ga and Al stabilized LLZO are identified as important factors in determining the electrochemical properties. The phase transition was located at an Al:Ga substitution ratio of 0.05:0.15 and is accompanied by a significant lowering of the activation energy for Li-ion transport to 0.26 eV. The phase transition combined with microstructural changes concomitant with an increase of the Ga/Al ratio continuously improves the Li-ion conductivity from 2.6 × 10–4 S cm–1 to 1.2 × 10–3 S cm–1, which is close to the calculated maximum for garnet-type materials. The increase in Ga content is also associated with better densification and smaller grains and is accompanied by a change in the area specific resistance (ASR) from 78 to 24 Ω cm2, the lowest reported value for LLZO so far. These results illustrate that understanding the structure–properties relationships in this class of materials allows practical obstacles to its utilization to be readily overcome. PMID:27110064

GaN as an interfacial passivation layer: tuning band offset and removing fermi level pinning for III-V MOS devices.

PubMed

Zhang, Zhaofu; Cao, Ruyue; Wang, Changhong; Li, Hao-Bo; Dong, Hong; Wang, Wei-Hua; Lu, Feng; Cheng, Yahui; Xie, Xinjian; Liu, Hui; Cho, Kyeongjae; Wallace, Robert; Wang, Weichao

2015-03-11

The use of an interfacial passivation layer is one important strategy for achieving a high quality interface between high-k and III-V materials integrated into high-mobility metal-oxide-semiconductor field-effect transistor (MOSFET) devices. Here, we propose gallium nitride (GaN) as the interfacial layer between III-V materials and hafnium oxide (HfO2). Utilizing first-principles calculations, we explore the structural and electronic properties of the GaN/HfO2 interface with respect to the interfacial oxygen contents. In the O-rich condition, an O8 interface (eight oxygen atoms at the interface, corresponding to 100% oxygen concentration) displays the most stability. By reducing the interfacial O concentration from 100 to 25%, we find that the interface formation energy increases; when sublayer oxygen vacancies exist, the interface becomes even less stable compared with O8. The band offset is also observed to be highly dependent on the interfacial oxygen concentration. Further analysis of the electronic structure shows that no interface states are present at the O8 interface. These findings indicate that the O8 interface serves as a promising candidate for high quality III-V MOS devices. Moreover, interfacial states are present when such interfacial oxygen is partially removed. The interface states, leading to Fermi level pinning, originate from unsaturated interfacial Ga atoms.

Stacking the Deck: Leveraging Surface Interactions to Tune Interfacial Electronic Structure

NASA Astrophysics Data System (ADS)

Maughan, Bret; Eads, Calley; Zahl, Percy; Sutter, Peter; Monti, Oliver

We present results from a series of experiments aimed at understanding and controlling molecular interactions in phthalocyanine (Pc) thin-films on Cu(110) to tailor the interfacial electronic structure. Using low-temperature scanning tunneling microscopy (LT-STM), we identify interactions that drive surface-molecule coupling, molecular self-assembly and thin-film order. We provide evidence that interactions with native Cu adatoms play a pivotal role in self-assembly of Pc systems, along with anisotropic nanoribbon growth dynamics, supported by an agent-based kinetic Monte Carlo (AB-KMC) simulation. We show further that self-assembled nanoribbon length can be controlled using surface diffusion barriers and that ordered 2D thin-film growth is promoted by diminishing surface-molecule interactions that otherwise dominate native Cu(110) interfaces. Altogether, this detailed structural understanding allows us to interpret interfacial electronic structure and dynamics, uncovered through ultraviolet (UPS) and two-photon photoemission (2PPE) spectroscopy experiments, in molecular configuration-specific detail. In all, our understanding of interfacial processes guides strategic modifications to both surface and molecule to harness interfacial interactions and thereby modify the collective electronic structure of the interface. NSF No. CHE-1213243 and No. CHE-1565497, Arizona TRIF, DOE/BNL Cntrct No. DE-SC0012704, and DOE No. DE-SC0016343.

Effect of high pressure homogenization on the structure and the interfacial and emulsifying properties of β-lactoglobulin.

PubMed

Ali, Ali; Le Potier, Isabelle; Huang, Nicolas; Rosilio, Véronique; Cheron, Monique; Faivre, Vincent; Turbica, Isabelle; Agnely, Florence; Mekhloufi, Ghozlene

2018-02-15

The effect of high pressure homogenization (HPH) on the structure of β-lactoglobulin (β-lg) was studied by combining spectroscopic, chromatographic, and electrophoretic methods. The consequences of the resulting structure modifications on oil/water (O/W) interfacial properties were also assessed. Moderated HPH treatment (100 MPa/4 cycles) showed no significant modification of protein structure and interfacial properties. However, a harsher HPH treatment (300 MPa/5 cycles) induced structural transformation, mainly from β-sheets to random coils, wide loss in lipocalin core, and protein aggregation via intermolecular disulfide bridges. HPH-modified β-lg displayed higher surface hydrophobicity leading to a faster adsorption rate at the interface and an earlier formation of an elastic interfacial film at C β-lg  = 0.1 wt%. However, no modification of the interfacial properties was observed at C β-lg  = 1 wt%. At this protein concentration, the prior denaturation of β-lg by HPH did not modify the droplet size of nanoemulsions prepared with these β-lg solutions as the aqueous phases. A slightly increased creaming rate was however observed. The effects of HPH and heat denaturations appeared qualitatively similar, but with differences in their extent. Copyright © 2017 Elsevier B.V. All rights reserved.

Correlating Humidity-Dependent Ionically Conductive Surface Area with Transport Phenomena in Proton-Exchange Membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Qinggang; Kusoglu, Ahmet; Lucas, Ivan T.

2011-08-01

The objective of this effort was to correlate the local surface ionic conductance of a Nafion? 212 proton-exchange membrane with its bulk and interfacial transport properties as a function of water content. Both macroscopic and microscopic proton conductivities were investigated at different relative humidity levels, using electrochemical impedance spectroscopy and current-sensing atomic force microscopy (CSAFM). We were able to identify small ion-conducting domains that grew with humidity at the surface of the membrane. Numerical analysis of the surface ionic conductance images recorded at various relative humidity levels helped determine the fractional area of ion-conducting active sites. A simple square-root relationshipmore » between the fractional conducting area and observed interfacial mass-transport resistance was established. Furthermore, the relationship between the bulk ionic conductivity and surface ionic conductance pattern of the Nafion? membrane was examined.« less

Enhancement of CNT/PET film adhesion by nano-scale modification for flexible all-solid-state supercapacitors

NASA Astrophysics Data System (ADS)

Kang, Yu Jin; Chung, Haegeun; Kim, Min-Seop; Kim, Woong

2015-11-01

We demonstrate the fabrication of high-integrity flexible supercapacitors using carbon nanotubes (CNTs), polyethylene terephthalate (PET) films, and ion gels. Although both CNTs and PET films are attractive materials for flexible electronics, they have poor adhesion properties. In this work, we significantly improve interfacial adhesion by introducing nanostructures at the interface of the CNT and PET layers. Simple reactive ion etching (RIE) of the PET substrates generates nano-scale roughness on the PET surface. RIE also induces hydrophilicity on the PET surface, which further enhances adhesive strength. The improved adhesion enables high integrity and excellent flexibility of the fabricated supercapacitors, demonstrated over hundreds of bending cycles. Furthermore, the supercapacitors show good cyclability with specific capacitance retention of 87.5% after 10,000 galvanostatic charge-discharge (GCD) cycles. Our demonstration may be important for understanding interfacial adhesion properties in nanoscale and for producing flexible, high-integrity, high-performance energy storage systems.

Spontaneous interfacial reaction between metallic copper and PBS to form cupric phosphate nanoflower and its enzyme hybrid with enhanced activity.

PubMed

He, Guangli; Hu, Weihua; Li, Chang Ming

2015-11-01

We herein report the spontaneous interfacial reaction between copper foil with 0.01 M phosphate buffered saline (PBS) to form free-standing cupric phosphate (Cu3(PO4)2) nanoflowers at ambient temperature. The underlying chemistry was thoroughly investigated and it is found that the formation of nanoflower is synergistically caused by dissolved oxygen, chlorine ions and phosphate ions. Enzyme-Cu3(PO4)2 hybrid nanoflower was further prepared successfully by using an enzyme-dissolving PBS solution and the enzymes in the hybrid exhibit enhanced biological activity. This work provides a facile route for large-scale synthesis of hierarchical inorganic and functional protein-inorganic hybrid architectures via a simple one-step solution-immersion reaction without using either template or surfactant, thus offering great potential for biosensing application among others. Copyright © 2015 Elsevier B.V. All rights reserved.

Origin of switching current transients in TIPS-pentacene based organic thin-film transistor with polymer dielectric

NASA Astrophysics Data System (ADS)

Singh, Subhash; Mohapatra, Y. N.

2017-06-01

We have investigated switch-on drain-source current transients in fully solution-processed thin film transistors based on 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) using cross-linked poly-4-vinylphenol as a dielectric. We show that the nature of the transient (increasing or decreasing) depends on both the temperature and the amplitude of the switching pulse at the gate. The isothermal transients are analyzed spectroscopically in a time domain to extract the degree of non-exponentiality and its possible origin in trap kinetics. We propose a phenomenological model in which the exchange of electrons between interfacial ions and traps controls the nature of the drain current transients dictated by the Fermi level position. The origin of interfacial ions is attributed to the essential fabrication step of UV-ozone treatment of the dielectric prior to semiconductor deposition.

Effects of nitrogen incorporation in HfO(2) grown on InP by atomic layer deposition: an evolution in structural, chemical, and electrical characteristics.

PubMed

Kang, Yu-Seon; Kim, Dae-Kyoung; Kang, Hang-Kyu; Jeong, Kwang-Sik; Cho, Mann-Ho; Ko, Dae-Hong; Kim, Hyoungsub; Seo, Jung-Hye; Kim, Dong-Chan

2014-03-26

We investigated the effects of postnitridation on the structural characteristics and interfacial reactions of HfO2 thin films grown on InP by atomic layer deposition (ALD) as a function of film thickness. By postdeposition annealing under NH3 vapor (PDN) at 600 °C, an InN layer formed at the HfO2/InP interface, and ionized NHx was incorporated in the HfO2 film. We demonstrate that structural changes resulting from nitridation of HfO2/InP depend on the film thickness (i.e., a single-crystal interfacial layer of h-InN formed at thin (2 nm) HfO2/InP interfaces, whereas an amorphous InN layer formed at thick (>6 nm) HfO2/InP interfaces). Consequently, the tetragonal structure of HfO2 transformed into a mixture structure of tetragonal and monoclinic because the interfacial InN layer relieved interfacial strain between HfO2 and InP. During postdeposition annealing (PDA) in HfO2/InP at 600 °C, large numbers of oxidation states were generated as a result of interfacial reactions between interdiffused oxygen impurities and out-diffused InP substrate elements. However, in the case of the PDN of HfO2/InP structures at 600 °C, nitrogen incorporation in the HfO2 film effectively blocked the out-diffusion of atomic In and P, thus suppressing the formation of oxidation states. Accordingly, the number of interfacial defect states (Dit) within the band gap of InP was significantly reduced, which was also supported by DFT calculations. Interfacial InN in HfO2/InP increased the electron-barrier height to ∼0.6 eV, which led to low-leakage-current density in the gate voltage region over 2 V.

A transmission electron microscopy and X-ray photoelectron spectroscopy study of annealing induced γ-phase nucleation, clustering, and interfacial dynamics in reactively sputtered amorphous alumina thin films

NASA Astrophysics Data System (ADS)

Kumar, A. K. Nanda; Prasanna, S.; Subramanian, B.; Jayakumar, S.; Rao, G. Mohan

2015-03-01

Pure α-Al2O3 exhibits a very high degree of thermodynamical stability among all metal oxides and forms an inert oxide scale in a range of structural alloys at high temperatures. We report that amorphous Al2O3 thin films sputter deposited over crystalline Si instead show a surprisingly active interface. On annealing, crystallization begins with nuclei of a phase closely resembling γ-Alumina forming almost randomly in an amorphous matrix, and with increasing frequency near the substrate/film interface. This nucleation is marked by the signature appearance of sharp (400) and (440) reflections and the formation of a diffuse diffraction halo with an outer maximal radius of ≈0.23 nm enveloping the direct beam. The microstructure then evolves by a cluster-coalescence growth mechanism suggestive of swift nucleation and sluggish diffusional kinetics, while locally the Al ions redistribute slowly from chemisorbed and tetrahedral sites to higher anion coordinated sites. Chemical state plots constructed from XPS data and simple calculations of the diffraction patterns from hypothetically distorted lattices suggest that the true origins of the diffuse diffraction halo are probably related to a complex change in the electronic structure spurred by the a-γ transformation rather than pure structural disorder. Concurrent to crystallization within the film, a substantially thick interfacial reaction zone also builds up at the film/substrate interface with the excess Al acting as a cationic source.

Role of Electrical Double Layer Structure in Ionic Liquid Gated Devices.

PubMed

Black, Jennifer M; Come, Jeremy; Bi, Sheng; Zhu, Mengyang; Zhao, Wei; Wong, Anthony T; Noh, Joo Hyon; Pudasaini, Pushpa R; Zhang, Pengfei; Okatan, Mahmut Baris; Dai, Sheng; Kalinin, Sergei V; Rack, Philip D; Ward, Thomas Zac; Feng, Guang; Balke, Nina

2017-11-22

Ionic liquid gating of transition metal oxides has enabled new states (magnetic, electronic, metal-insulator), providing fundamental insights into the physics of strongly correlated oxides. However, despite much research activity, little is known about the correlation of the structure of the liquids in contact with the transition metal oxide surface, its evolution with the applied electric potential, and its correlation with the measured electronic properties of the oxide. Here, we investigate the structure of an ionic liquid at a semiconducting oxide interface during the operation of a thin film transistor where the electrical double layer gates the device using experiment and theory. We show that the transition between the ON and OFF states of the amorphous indium gallium zinc oxide transistor is accompanied by a densification and preferential spatial orientation of counterions at the oxide channel surface. This process occurs in three distinct steps, corresponding to ion orientations, and consequently, regimes of different electrical conductivity. The reason for this can be found in the surface charge densities on the oxide surface when different ion arrangements are present. Overall, the field-effect gating process is elucidated in terms of the interfacial ionic liquid structure, and this provides unprecedented insight into the working of a liquid gated transistor linking the nanoscopic structure to the functional properties. This knowledge will enable both new ionic liquid design as well as advanced device concepts.

Role of Electrical Double Layer Structure in Ionic Liquid Gated Devices

DOE PAGES

Black, Jennifer M.; Come, Jeremy; Bi, Sheng; ...

2017-10-24

Ionic liquid gating of transition metal oxides has enabled new states (magnetic, electronic, metal–insulator), providing fundamental insights into the physics of strongly correlated oxides. However, despite much research activity, little is known about the correlation of the structure of the liquids in contact with the transition metal oxide surface, its evolution with the applied electric potential, and its correlation with the measured electronic properties of the oxide. Here, we investigate the structure of an ionic liquid at a semiconducting oxide interface during the operation of a thin film transistor where the electrical double layer gates the device using experiment andmore » theory. We show that the transition between the ON and OFF states of the amorphous indium gallium zinc oxide transistor is accompanied by a densification and preferential spatial orientation of counterions at the oxide channel surface. This process occurs in three distinct steps, corresponding to ion orientations, and consequently, regimes of different electrical conductivity. The reason for this can be found in the surface charge densities on the oxide surface when different ion arrangements are present. Overall, the field-effect gating process is elucidated in terms of the interfacial ionic liquid structure, and this provides unprecedented insight into the working of a liquid gated transistor linking the nanoscopic structure to the functional properties. This knowledge will enable both new ionic liquid design as well as advanced device concepts.« less

Role of Electrical Double Layer Structure in Ionic Liquid Gated Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Black, Jennifer M.; Come, Jeremy; Bi, Sheng

Ionic liquid gating of transition metal oxides has enabled new states (magnetic, electronic, metal–insulator), providing fundamental insights into the physics of strongly correlated oxides. However, despite much research activity, little is known about the correlation of the structure of the liquids in contact with the transition metal oxide surface, its evolution with the applied electric potential, and its correlation with the measured electronic properties of the oxide. Here, we investigate the structure of an ionic liquid at a semiconducting oxide interface during the operation of a thin film transistor where the electrical double layer gates the device using experiment andmore » theory. We show that the transition between the ON and OFF states of the amorphous indium gallium zinc oxide transistor is accompanied by a densification and preferential spatial orientation of counterions at the oxide channel surface. This process occurs in three distinct steps, corresponding to ion orientations, and consequently, regimes of different electrical conductivity. The reason for this can be found in the surface charge densities on the oxide surface when different ion arrangements are present. Overall, the field-effect gating process is elucidated in terms of the interfacial ionic liquid structure, and this provides unprecedented insight into the working of a liquid gated transistor linking the nanoscopic structure to the functional properties. This knowledge will enable both new ionic liquid design as well as advanced device concepts.« less

Interfacial Tension in the CaO-Al2O3-SiO2-(MgO) Liquid Slag-Solid Oxide Systems

NASA Astrophysics Data System (ADS)

Abdeyazdan, Hamed; Monaghan, Brian J.; Longbottom, Raymond J.; Rhamdhani, M. Akbar; Dogan, Neslihan; Chapman, Michael W.

2017-08-01

Interfacial phenomenon is critical in metal processing and refining. While it is known to be important, there are little data available for key oxide systems in the literature. In this study, the interfacial tension ( σ LS) of liquid slag on solid oxides (alumina, spinel, and calcium aluminate), for a range of slags in the CaO-Al2O3-SiO2-(MgO) system at 1773 K (1500 °C), has been evaluated. The results show that basic ladle-type slags exhibit lower σ LS with oxide phases examined compared to that of acid tundish-type slags. Also, within the slag types (acid and base), σ LS was observed to decrease with increasing slag basicity. A correlation between σ LS and slag structure was observed, i.e., σ LS was found to decrease linearly with increasing of slag optical basicity (Λ) and decrease logarithmically with decreasing of slag viscosity from acid to base slags. This indicated a higher σ LS as the ions in the slag become larger and more complex. Through a work of adhesion ( W) analysis, it was shown that basic ladle slags with lower σ LS result in a greater W, i.e., form a stronger bond with the solid oxide phases examined. This indicates that all other factors being equal, the efficiency of inclusion removal from steel of inclusions of similar phase to these solid oxides would be greater.

Controlling Interfacial Separation in Porous Structures by Void Patterning

NASA Astrophysics Data System (ADS)

Ghareeb, Ahmed; Elbanna, Ahmed

Manipulating interfacial response for enhanced adhesion or fracture resistance is a problem of great interest to scientists and engineers. In many natural materials and engineering applications, an interface exists between a porous structure and a substrate. A question that arises is how the void distribution in the bulk may affect the interfacial response and whether it is possible to alter the interfacial toughness without changing the surface physical chemistry. In this paper, we address this question by studying the effect of patterning voids on the interfacial-to-the overall response of an elastic plate glued to a rigid substrate by bilinear cohesive material. Different patterning categories are investigated; uniform, graded, and binary voids. Each case is subjected to upward displacement at the upper edge of the plate. We show that the peak force and maximum elongation at failure depend on the voids design and by changing the void size, alignment or gradation we may control these performance measures. We relate these changes in the measured force displacement response to energy release rate as a measure of interfacial toughness. We discuss the implications of our results on design of bulk heterogeneities for enhanced interfacial behavior.

Formation of Reversible Solid Electrolyte Interface on Graphite Surface from Concentrated Electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Dongping; Tao, Jinhui; Yan, Pengfei

2017-02-10

Interfacial phenomena have always been key determinants for the performance of energy storage technologies. The solid electrolyte interfacial (SEI) layer, pervasive on the surfaces of battery electrodes for numerous chemical couples, directly affects the ion transport, charge transfer and lifespan of the entire energy system. Almost all SEI layers, however, are unstable resulting in the continuous consumption of the electrolyte. Typically, this leads to the accumulation of degradation products on/restructuring of the electrode surface and thus increased cell impedance, which largely limits the long-term operation of the electrochemical reactions. Herein, a completely new SEI formation mechanism has been discovered, inmore » which the electrolyte components reversibly self-assemble into a protective surface coating on a graphite electrode upon changing the potential. In contrast to the established wisdom regarding the necessity of employing the solvent ethylene carbonate (EC) to form a protective SEI layer on graphite, a wide range of EC-free electrolytes are demonstrated for the reversible intercalation/deintercalation of Li+ cations within a graphite lattice, thereby providing tremendous flexibility in electrolyte tailoring for battery couples. This novel finding is broadly applicable and provides guidance for how to control interfacial reactions through the relationship between ion aggregation and solvent decomposition at polarized interfaces.« less

Ion Beam Assisted Deposition of Thin Epitaxial GaN Films.

PubMed

Rauschenbach, Bernd; Lotnyk, Andriy; Neumann, Lena; Poppitz, David; Gerlach, Jürgen W

2017-06-23

The assistance of thin film deposition with low-energy ion bombardment influences their final properties significantly. Especially, the application of so-called hyperthermal ions (energy <100 eV) is capable to modify the characteristics of the growing film without generating a large number of irradiation induced defects. The nitrogen ion beam assisted molecular beam epitaxy (ion energy <25 eV) is used to deposit GaN thin films on (0001)-oriented 6H-SiC substrates at 700 °C. The films are studied in situ by reflection high energy electron diffraction, ex situ by X-ray diffraction, scanning tunnelling microscopy, and high-resolution transmission electron microscopy. It is demonstrated that the film growth mode can be controlled by varying the ion to atom ratio, where 2D films are characterized by a smooth topography, a high crystalline quality, low biaxial stress, and low defect density. Typical structural defects in the GaN thin films were identified as basal plane stacking faults, low-angle grain boundaries forming between w-GaN and z-GaN and twin boundaries. The misfit strain between the GaN thin films and substrates is relieved by the generation of edge dislocations in the first and second monolayers of GaN thin films and of misfit interfacial dislocations. It can be demonstrated that the low-energy nitrogen ion assisted molecular beam epitaxy is a technique to produce thin GaN films of high crystalline quality.

Smooth Interfacial Scavenging for Resistive Switching Oxide via the Formation of Highly Uniform Layers of Amorphous TaOx.

PubMed

Tsurumaki-Fukuchi, Atsushi; Nakagawa, Ryosuke; Arita, Masashi; Takahashi, Yasuo

2018-02-14

We demonstrate that the inclusion of a Ta interfacial layer is a remarkably effective strategy for forming interfacial oxygen defects at metal/oxide junctions. The insertion of an interfacial layer of a reactive metal, that is, a "scavenging" layer, has been recently proposed as a way to create a high concentration of oxygen defects at an interface in redox-based resistive switching devices, and growing interest has been given to the underlying mechanism. Through structural and chemical analyses of Pt/metal/SrTiO 3 /Pt structures, we reveal that the rate and amount of oxygen scavenging are not directly determined by the formation free energies in the oxidation reactions of the scavenging metal and unveil the important roles of oxygen diffusibility. Active oxygen scavenging and highly uniform oxidation via scavenging are revealed for a Ta interfacial layer with high oxygen diffusibility. In addition, the Ta scavenging layer is shown to exhibit a highly uniform structure and to form a very flat interface with SrTiO 3 , which are advantageous for the fabrication of a steep metal/oxide contact.

Experimental study on interfacial area transport in downward two-phase flow

NASA Astrophysics Data System (ADS)

Wang, Guanyi

In view of the importance of two group interfacial area transport equations and lack of corresponding accurate downward flow database that can reveal two group interfacial area transport, a systematic database for adiabatic, air-water, vertically downward two-phase flow in a round pipe with inner diameter of 25.4 mm was collected to gain an insight of interfacial structure and provide benchmarking data for two-group interfacial area transport models. A four-sensor conductivity probe was used to measure the local two phase flow parameters and data was collected with data sampling frequency much higher than conventional data sampling frequency to ensure the accuracy. Axial development of local flow parameter profiles including void fraction, interfacial area concentration, and Sauter mean diameter were presented. Drastic inter-group transfer of void fraction and interfacial area was observed at bubbly to slug transition flow. And the wall peaked interfacial area concentration profiles were observed in churn-turbulent flow. The importance of local data about these phenomenon on flow structure prediction and interfacial area transport equation benchmark was analyzed. Bedsides, in order to investigate the effect of inlet conditions, all experiments were repeated after installing the flow straightening facility, and the results were briefly analyzed. In order to check the accuracy of current data, the experiment results were cross-checked with rotameter measurement as well as drift-flux model prediction, the averaged error is less than 15%. Current models for two-group interfacial area transport equation were evaluated using these data. The results show that two-group interfacial area transport equations with current models can predict most flow conditions with error less than 20%, except some bubbly to slug transition flow conditions and some churn-turbulent flow conditions. The disagreement between models and experiments could result from underestimate of inter-group void transfer.

Insights on synergy of materials and structures in biomimetic platelet-matrix composites

NASA Astrophysics Data System (ADS)

Sakhavand, Navid; Shahsavari, Rouzbeh

2018-01-01

Hybrid materials such as biomimetic platelet-matrix composites are in high demand to confer low weight and multifunctional mechanical properties. This letter reports interfacial-bond regulated assembly of polymers on cement-an archetype model with significant infrastructure applications. We demonstrate a series of 20+ molecular dynamics studies on decoding and optimizing the complex interfacial interactions including the role and types of various heterogeneous, competing interfacial bonds that are key to adhesion and interfacial strength. Our results show an existence of an optimum overlap length scale (˜15 nm) between polymers and cement crystals, exhibiting the best balance of strength, toughness, stiffness, and ductility for the composite. This finding, combined with the fundamental insights into the nature of interfacial bonds, provides key hypotheses for selection and processing of constituents to deliberate the best synergy in the structure and materials of platelet-matrix composites.

Thermal Transport at Solid-Liquid Interfaces: High Pressure Facilitates Heat Flow through Nonlocal Liquid Structuring.

PubMed

Han, Haoxue; Mérabia, Samy; Müller-Plathe, Florian

2017-05-04

The integration of three-dimensional microelectronics is hampered by overheating issues inherent to state-of-the-art integrated circuits. Fundamental understanding of heat transfer across soft-solid interfaces is important for developing efficient heat dissipation capabilities. At the microscopic scale, the formation of a dense liquid layer at the solid-liquid interface decreases the interfacial heat resistance. We show through molecular dynamics simulations of n-perfluorohexane on a generic wettable surface that enhancement of the liquid structure beyond a single adsorbed layer drastically enhances interfacial heat conductance. Pressure is used to control the extent of the liquid layer structure. The interfacial thermal conductance increases with pressure values up to 16.2 MPa at room temperature. Furthermore, it is shown that liquid structuring enhances the heat-transfer rate of high-energy lattice waves by broadening the transmission peaks in the heat flux spectrum. Our results show that pressure is an important external parameter that may be used to control interfacial heat conductance at solid-soft interfaces.

Molecular dynamics simulations of lithium silicate/vanadium pentoxide interfacial lithium ion diffusion in thin film lithium ion-conducting devices

NASA Astrophysics Data System (ADS)

Li, Weiqun

The lithium ion diffusion behavior and mechanism in the glassy electrolyte and the electrolyte/cathode interface during the initial stage of lithium ion diffusing from electrolyte into cathode were investigated using Molecular Dynamics simulation technique. Lithium aluminosilicate glass electrolytes with different R (ratio of the concentration of Al to Li) were simulated. The structural features of the simulated glasses are analyzed using Radial Distribution Function (RDF) and Pair Distribution Function (PDF). The diffusion coefficient and activation energy of lithium ion diffusion in simulated lithium aluminosilicate glasses were calculated and the values are consistent with those in experimental glasses. The behavior of lithium ion diffusion from the glassy electrolyte into a polycrystalline layered intercalation cathode has been studied. The solid electrolyte was a model lithium silicate glass while the cathode was a nanocrystalline vanadia with amorphous V2O5 intergranular films (IGF) between the V2O5 crystals. Two different orientations between the V2O5 crystal planes are presented for lithium ion intercalation via the amorphous vanadia IGF. A series of polycrystalline vanadia cathodes with 1.3, 1.9, 2.9 and 4.4 nm thickness IGFs were simulated to examine the effects of the IGF thickness on lithium ion transport in the polycrystalline vanadia cathodes. The simulated results showed that the lithium ions diffused from the glassy electrolyte into the IGF of the polycrystalline vanadia cathode and then part of those lithium ions diffused into the crystalline V2O5 from the IGF. The simulated results also showed an ordering of the vanadium ion structure in the IGF near the IGF/V2 O5 interface. The ordering structure still existed with glass former silica additive in IGF. Additionally, 2.9 run is suggested to be the optimal thickness of the IGF, which is neither too thick to decrease the capacity of the cathode nor too thin to impede the transport of lithium from glassy electrolyte into the cathode. Parallel molecular dynamic simulation technique was also used for a larger electrolyte/cathode interface system, which include more atoms and more complicated microstructures. Simulation results from larger electrolyte/cathode interface system prove that there is no size effect on simulation of smaller electrolyte/cathode interface system from statistical point of view.

Oxidized film structure and method of making epitaxial metal oxide structure

DOEpatents

Gan, Shupan [Richland, WA; Liang, Yong [Richland, WA

2003-02-25

A stable oxidized structure and an improved method of making such a structure, including an improved method of making an interfacial template for growing a crystalline metal oxide structure, are disclosed. The improved method comprises the steps of providing a substrate with a clean surface and depositing a metal on the surface at a high temperature under a vacuum to form a metal-substrate compound layer on the surface with a thickness of less than one monolayer. The compound layer is then oxidized by exposing the compound layer to essentially oxygen at a low partial pressure and low temperature. The method may further comprise the step of annealing the surface while under a vacuum to further stabilize the oxidized film structure. A crystalline metal oxide structure may be subsequently epitaxially grown by using the oxidized film structure as an interfacial template and depositing on the interfacial template at least one layer of a crystalline metal oxide.

Deconstructing Temperature Gradients across Fluid Interfaces: The Structural Origin of the Thermal Resistance of Liquid-Vapor Interfaces

NASA Astrophysics Data System (ADS)

Muscatello, Jordan; Chacón, Enrique; Tarazona, Pedro; Bresme, Fernando

2017-07-01

The interfacial thermal resistance determines condensation-evaporation processes and thermal transport across material-fluid interfaces. Despite its importance in transport processes, the interfacial structure responsible for the thermal resistance is still unknown. By combining nonequilibrium molecular dynamics simulations and interfacial analyses that remove the interfacial thermal fluctuations we show that the thermal resistance of liquid-vapor interfaces is connected to a low density fluid layer that is adsorbed at the liquid surface. This thermal resistance layer (TRL) defines the boundary where the thermal transport mechanism changes from that of gases (ballistic) to that characteristic of dense liquids, dominated by frequent particle collisions involving very short mean free paths. We show that the thermal conductance is proportional to the number of atoms adsorbed in the TRL, and hence we explain the structural origin of the thermal resistance in liquid-vapor interfaces.

Strong cooperative effect of oppositely charged surfactant mixtures on their adsorption and packing at the air-water interface and interfacial water structure.

PubMed

Nguyen, Khoi T; Nguyen, Tuan D; Nguyen, Anh V

2014-06-24

Remarkable adsorption enhancement and packing of dilute mixtures of water-soluble oppositely-charged surfactants, sodium dodecyl sulfate (SDS) and dodecyl amine hydrochloride (DAH), at the air-water interface were observed by using sum frequency generation spectroscopy and tensiometry. The interfacial water structure was also observed to be significantly influenced by the SDS-DAH mixtures, differently from the synergy of the single surfactants. Most strikingly, the obtained spectroscopic evidence suggests that the interfacial hydrophobic alkyl chains of the binary mixtures assemble differently from those of single surfactants. This study highlights the significance of the cooperative interaction between the headgroups of oppositely charged binary surfactant systems and subsequently provides some insightful observations about the molecular structure of the air-aqueous interfacial water molecules and, more importantly, about the packing nature of the surfactant hydrophobic chains of dilute SDS-DAH mixtures of concentration below 1% of the CMC.

Tunable dielectric response and electronic conductivity of potassium-ion-doped tunnel-structured manganese oxides

NASA Astrophysics Data System (ADS)

He, Gaihua; Duan, Yuping; Song, Lulu; Zhang, Xuefeng

2018-06-01

Potassium-ion-doped MnO2 has been successfully synthesized using the hydrothermal method, and the influence of the doped potassium ions on the electrical conductivity and permittivity is studied. X-ray powder diffraction, scanning electron microscopy, electron-probe micro-analysis, and a vector network analyzer are used to perform characterization. The densities of states of doped and undoped MnO2 tunnel structures are also discussed based on first-principles calculations. Results show that the conductivity and dielectric resonance of MnO2 can be elevated by means of K+ doping. The conductivity of K+-doped MnO2 prepared at different reaction times shows a decreasing trend and is generally 1 order of magnitude higher than that of pure MnO2. The electrical conductivity of K+-doped MnO2 (R3) shows the highest value of 3.33 × 10-2 S/cm at the reaction time of 24 h, while that of pure MnO2 is 8.50 × 10-4 S/cm. When treated with acid, the conductivity of samples remains basically stable along with the increase of treatment time. In addition, acid treatment plays a very significant role in controlling the amount of K+ ions in crystals. The K+ contents of acid-treated samples are 5 times lower than that of the untreated R1. The dielectric losses of the samples with different reaction times are enhanced markedly with frequency increment. The complex permittivity of pure MnO2 only exhibits a resonance at ˜12 GHz, while K+-doped MnO2 exhibits another resonance behavior at ˜9 GHz. The capacity of the dielectric property in the net structure is enhanced by the interfacial polarization, dielectric relaxation, multiple internal reflections, and multiple scattering benefiting.

Investigations of the structure and "interfacial" surface chemistry of Bioglass (RTM) materials by solid-state multinuclear NMR spectroscopy

NASA Astrophysics Data System (ADS)

Sarkar, Gautam

Bioactive materials such as BioglassRTM 45S5 (45% SiO 2, 24.5% CaO, 24.5% Na2O, and 6% P2O5 by weight) are sodium-phosphosilicate glasses containing independent three-dimensional silicate and phosphate networks and Na+ and Ca2+ ions as modifying cations. Due to their bioactivity, these materials are currently used as implants and for other surgical and clinical applications. The bioactivity of BioglassesRTM is due to their unique capability to form chemical bonds to tissues through an octacalciumphosphate (OCP)- and/or hydroxyapatite-like (HA) "interfacial" matrix. The formation of OCP and/or HA is preceded by the formation of a silica-rich surface layer and the subsequent growth of an amorphous calcium phosphate (a-CP) layer. Structural characterization of a series of commercial and synthesized Bioglass materials 45S5 52S, 55S, 60S, and synthesized 17O-labelled "Bioglass materials 45S, 52S, 55S and 60S" have been obtained using solid-state single-pulse magic-angle spinning (SP/MAS) 17O, 23Na, 29Si and 31P NMR. The 17O NMR isotropic chemical shifts and estimates of the quadrupole coupling constants (Cq) [at fixed asymmetry parameter ( hQ ) values of zero] have been obtained from solid-state spin-echo 17O SP/MAS NMR spectra of 17O-labelled "Bioglasses". The simulation results of these spectra reveal the presence of both bridging-oxygens (BO, i.e. ≡ Si-17OSi ≡ ) and non-bridging oxygens (NBO, i.e. ≡ Si-17O-Na+/Ca2+ ) in the silicate networks in these materials. 17O NMR spectra of these Bioglass materials do not show any direct evidence for the presence of BO and NBO atoms in the phosphate units; however, they are expected to be present in small amounts. In vitro reactions of BioglassRTM 45S5, 60S and 77S powders have been used to study the "interfacial" surface chemistry of these materials in simulated body-fluid (SBF, Kyoto or K9 solution) and/or 17O-enriched tris-buffer solution. 29Si and 31P SP/MAS NMR have been used to identify and quantify the extent of formation of surface silica species and follow the formation of phosphate species, respectively, while cross-polarization magic-angle spinning (CP/MAS) 29Si and 31P NMR have provided information about low intensity NMR peaks due to various silicon- and phosphorus-species present in the vicinity of associated protons on the surface of in vitro reacted BioglassRTM materials. The solid-state NMR investigations of the "interfacial" surface reactions of BioglassRTM materials are discussed in the context of the structure of these materials and the influence of this structure on the kinetics and the mechanism of their "interfacial" surface chemistry. (Abstract shortened by UMI.) BioglassRTM, trademark, University of Florida, Gainesville, FL, 32611.

Modelling of AlAs/GaAs interfacial structures using high-angle annular dark field (HAADF) image simulations.

PubMed

Robb, Paul D; Finnie, Michael; Craven, Alan J

2012-07-01

High angle annular dark field (HAADF) image simulations were performed on a series of AlAs/GaAs interfacial models using the frozen-phonon multislice method. Three general types of models were considered-perfect, vicinal/sawtooth and diffusion. These were chosen to demonstrate how HAADF image measurements are influenced by different interfacial structures in the technologically important III-V semiconductor system. For each model, interfacial sharpness was calculated as a function of depth and compared to aberration-corrected HAADF experiments of two types of AlAs/GaAs interfaces. The results show that the sharpness measured from HAADF imaging changes in a complicated manner with thickness for complex interfacial structures. For vicinal structures, it was revealed that the type of material that the probe projects through first of all has a significant effect on the measured sharpness. An increase in the vicinal angle was also shown to generate a wider interface in the random step model. The Moison diffusion model produced an increase in the interface width with depth which closely matched the experimental results of the AlAs-on-GaAs interface. In contrast, the interface width decreased as a function of depth in the linear diffusion model. Only in the case of the perfect model was it possible to ascertain the underlying structure directly from HAADF image analysis. Copyright © 2012 Elsevier B.V. All rights reserved.

Author Correction: Decoupling electron and ion storage and the path from interfacial storage to artificial electrodes

NASA Astrophysics Data System (ADS)

Chen, Chia-Chin; Maier, Joachim

2018-05-01

In the version of this Perspective originally published, in the sentence "It is worthy of note that the final LiF-free situation characterized by MnO taking up the holes and the (F- containing) MnO surface taking up the lithium ions is also a subcase of the job-sharing concept23.", the word `holes' should have been `electrons'. This has now been corrected.

Defect interactions with stepped CeO₂/SrTiO₃ interfaces: implications for radiation damage evolution and fast ion conduction.

PubMed

Dholabhai, Pratik P; Aguiar, Jeffery A; Misra, Amit; Uberuaga, Blas P

2014-05-21

Due to reduced dimensions and increased interfacial content, nanocomposite oxides offer improved functionalities in a wide variety of advanced technological applications, including their potential use as radiation tolerant materials. To better understand the role of interface structures in influencing the radiation damage tolerance of oxides, we have conducted atomistic calculations to elucidate the behavior of radiation-induced point defects (vacancies and interstitials) at interface steps in a model CeO2/SrTiO3 system. We find that atomic-scale steps at the interface have substantial influence on the defect behavior, which ultimately dictate the material performance in hostile irradiation environments. Distinctive steps react dissimilarly to cation and anion defects, effectively becoming biased sinks for different types of defects. Steps also attract cation interstitials, leaving behind an excess of immobile vacancies. Further, defects introduce significant structural and chemical distortions primarily at the steps. These two factors are plausible origins for the enhanced amorphization at steps seen in our recent experiments. The present work indicates that comprehensive examination of the interaction of radiation-induced point defects with the atomic-scale topology and defect structure of heterointerfaces is essential to evaluate the radiation tolerance of nanocomposites. Finally, our results have implications for other applications, such as fast ion conduction.

Surface and buried interfacial structures of epoxy resins used as underfills studied by sum frequency generation vibrational spectroscopy.

PubMed

Vázquez, Anne V; Holden, Brad; Kristalyn, Cornelius; Fuller, Mike; Wilkerson, Brett; Chen, Zhan

2011-05-01

Flip chip technology has greatly improved the performance of semiconductor devices, but relies heavily on the performance of epoxy underfill adhesives. Because epoxy underfills are cured in situ in flip chip semiconductor devices, understanding their surface and interfacial structures is critical for understanding their adhesion to various substrates. Here, sum frequency generation (SFG) vibrational spectroscopy was used to study surface and buried interfacial structures of two model epoxy resins used as underfills in flip chip devices, bisphenol A digylcidyl ether (BADGE) and 1,4-butanediol diglycidyl ether (BDDGE). The surface structures of these epoxies were compared before and after cure, and the orientations of their surface functional groups were deduced to understand how surface structural changes during cure may affect adhesion properties. Further, the effect of moisture exposure, a known cause of adhesion failure, on surface structures was studied. It was found that the BADGE surface significantly restructured upon moisture exposure while the BDDGE surface did not, showing that BADGE adhesives may be more prone to moisture-induced delamination. Lastly, although surface structure can give some insight into adhesion, buried interfacial structures more directly correspond to adhesion properties of polymers. SFG was used to study buried interfaces between deuterated polystyrene (d-PS) and the epoxies before and after moisture exposure. It was shown that moisture exposure acted to disorder the buried interfaces, most likely due to swelling. These results correlated with lap shear adhesion testing showing a decrease in adhesion strength after moisture exposure. The presented work showed that surface and interfacial structures can be correlated to adhesive strength and may be helpful in understanding and designing optimized epoxy underfill adhesives.

Collaborative Research and Development (CR&D) III Task Order 0077: Fundamental Studies of Plasticity, Interfacial Boundaries and Liquid Metals

DTIC Science & Technology

2013-06-01

Interfacial Boundaries and Liquid Metals Dallas Trinkle Independent Contractor JUNE 2013 Final Report Approved for public...SIGNATURE//_________________ CHRISTOPHER WOODWARD, Project Engineer DANIEL EVANS, Chief Metals Branch Metals Branch Structural ...Materials Division Structural Materials Division ____//SIGNATURE//___________________ ROBERT T. MARSHALL, Deputy Chief

Detection of amide I signals of interfacial proteins in situ using SFG.

PubMed

Wang, Jie; Even, Mark A; Chen, Xiaoyun; Schmaier, Alvin H; Waite, J Herbert; Chen, Zhan

2003-08-20

In this Communication, we demonstrate the novel observation that it is feasible to collect amide signals from polymer/protein solution interfaces in situ using sum frequency generation (SFG) vibrational spectroscopy. Such SFG amide signals allow for acquisition of more detailed molecular level information of entire interfacial protein structures. Proteins investigated include bovine serum albumin, mussel protein mefp-2, factor XIIa, and ubiquitin. Our studies indicate that different proteins generate different SFG amide signals at the polystyrene/protein solution interface, showing that they have different interfacial coverage, secondary structure, or orientation.

Atomic structure and bonding of the interfacial bilayer between Au nanoparticles and epitaxially regrown MgAl{sub 2}O{sub 4} substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Guo-zhen; Canadian Centre of Electron Microscopy and Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1; Majdi, Tahereh

2014-12-08

A unique metal/oxide interfacial bilayer formed between Au nanoparticles and MgAl{sub 2}O{sub 4} substrates following thermal treatment is reported. Associated with the formation of the bilayer was the onset of an abnormal epitaxial growth of the substrate under the nanoparticle. According to the redistribution of atoms and the changes of their electronic structure probed across the interface by a transmission electron microscopy, we suggest two possible atomic models of the interfacial bilayer.

The influence of interfacial energies and gravitational levels on the directionally solidified structures in hypermonotectic alloys

NASA Technical Reports Server (NTRS)

Andrews, J. B.; Curreri, P. A.; Sandlin, A. C.

1988-01-01

Various Cu-Pb-Al alloys were directionally solidified under 1-g conditions and alternating high-g/low-g conditions (achieved using NSAS's KC-135 aircraft) as a means of studying the influence of interfacial energies and gravitational levels on the resulting microstructures. Directional solidification of low Al content alloys was found to result in samples with coarser more irregular microstructures than in alloys with high Al contents under all the gravity conditions considered. Structures are correlated with interfacial energies, growth rates, and gravitational levels.

Controls of ionic strength and macromolecule chemistry on calcite nucleation: Salinity and ion hydration as levers for regulating biomineralization

NASA Astrophysics Data System (ADS)

Dove, P. M.; Giuffre, A. J.; Mergelsberg, S. T.; Han, N.; De Yoreo, J. J.

2016-12-01

Organisms form shells and skeletons with remarkable fidelity by controlling the timing and placement of the minerals that nucleate and subsequently grow. An extensive effort has identified features of the organic matrix that regulate this process. Recent measurements from our group show the energy barrier to nucleation onto polysaccharide (PS) substrates is dependent upon hydrophilicity through functional group chemistry and suggest that free energy of the macromolecule-liquid interface influences where and when mineral nucleation occurs (Giuffre et al., 2013, PNAS). The importance of interfacial free energy in regulating nucleation raises the question of whether local changes in salinity or electrolyte composition can be tuned to further modulate the onset of calcite nucleation. Using alginate (negatively charged by carboxyl groups) and chitosan (small positive charge by amine groups), the rate of calcite nucleation was measured at controlled supersaturations and pH as a function of NaCl concentration (65-600 mM). Analyses of the data show the thermodynamic barrier to calcite nucleation onto both types of PS increases with ionic strength. The evidence suggests this effect arises from an increasing concentration of solvated ions at the PS-water interface while also increasing the hydrophilic character of that interface; thus decreasing the substrate-liquid interfacial free energy. To test this explanation, a second group of nucleation experiments used a suite of electrolytes (alkali chlorides for alginate and sodium halides for chitosan) while holding ionic strength constant. Indeed, the nucleation barriers for calcite formation are electrolyte-specific and correlated with the hydration free energy of the ion. This suggests solvated electrolyte ions indirectly regulate calcite nucleation onto substrates through their competition with the substrate for water thereby influencing net interfacial free energy. These effects are consistent with the long-established salting-in phenomena of the Hofmeister series. The new insights from this experimental study reiterate the importance of electrolytes in reactions involving mineral-water interfaces and suggest a role for seemingly inert `spectator' ions in regulating the local timing and placement of minerals during biomineralization.

Interfacial Reactivity Benchmarking of the Sodium Ion Conductors Na3PS4 and Sodium β-Alumina for Protected Sodium Metal Anodes and Sodium All-Solid-State Batteries.

PubMed

Wenzel, Sebastian; Leichtweiss, Thomas; Weber, Dominik A; Sann, Joachim; Zeier, Wolfgang G; Janek, Jürgen

2016-10-05

The interfacial stability of solid electrolytes at the electrodes is crucial for an application of all-solid-state batteries and protected electrodes. For instance, undesired reactions between sodium metal electrodes and the solid electrolyte form charge transfer hindering interphases. Due to the resulting large interfacial resistance, the charge transfer kinetics are altered and the overvoltage increases, making the interfacial stability of electrolytes the limiting factor in these systems. Driven by the promising ionic conductivities of Na 3 PS 4 , here we explore the stability and viability of Na 3 PS 4 as a solid electrolyte against metallic Na and compare it to that of Na-β″-Al 2 O 3 (sodium β-alumina). As expected, Na-β″-Al 2 O 3 is stable against sodium, whereas Na 3 PS 4 decomposes with an increasing overall resistance, making Na-β″-Al 2 O 3 the electrolyte of choice for protected sodium anodes and all-solid-state batteries.

Interface-Assisted Synthesis of 2D Materials: Trend and Challenges.

PubMed

Dong, Renhao; Zhang, Tao; Feng, Xinliang

2018-06-18

The discovery of graphene one decade ago has triggered enormous interest in developing two-dimensional materials (2DMs)-that is 2D allotropes of various elements or compounds (consisting of two or more covalently bonded elements) or molecular frameworks with periodic structures. At present, various synthesis strategies have been exploited to produce 2DMs, such as top-down exfoliation and bottom-up chemical vapor deposition and solution synthesis methods. In this review article, we will highlight the interfacial roles toward the controlled synthesis of inorganic and organic 2DMs with varied structural features. We will summarize the state-of-the-art progress on interfacial synthesis strategies and address their advancements in the structural, morphological, and crystalline control by the direction of the arrangement of the molecules or precursors at a confined 2D space. First, we will provide an overview of the interfaces and introduce their advantages and uniqueness for the synthesis of 2DMs, followed by a brief classification of inorganic and organic 2DMs achieved by interfacial synthesis. Next, the currently developed interfacial synthesis strategies combined with representative inorganic and organic 2DMs are summarized, including the description of method details, the corresponding structural features, and the insights into the advantages and limitations of the synthesis methods, along with some recommendable characterization methods for understanding the interfacial assembly of the precursors and crystal growth of 2DMs. After that, we will discuss several classes of emerging organic 2DMs with particular emphasis on the structural control by the interfacial synthesis strategies. Note that, inorganic 2DMs will not be categorized separately due to the fact that a number of review articles have covered the synthesis, structure, processing, and applications. Finally, the challenges and perspectives are provided regarding the future development of interface-assisted synthesis of 2DMs with diverse structural and functional control.

Complexation-induced supramolecular assembly drives metal-ion extraction.

PubMed

Ellis, Ross J; Meridiano, Yannick; Muller, Julie; Berthon, Laurence; Guilbaud, Philippe; Zorz, Nicole; Antonio, Mark R; Demars, Thomas; Zemb, Thomas

2014-09-26

Combining experiment with theory reveals the role of self-assembly and complexation in metal-ion transfer through the water-oil interface. The coordinating metal salt Eu(NO3)3 was extracted from water into oil by a lipophilic neutral amphiphile. Molecular dynamics simulations were coupled to experimental spectroscopic and X-ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the organic phase combine with long-range interactions to produce spontaneous changes in the solvent microstructure. Extraction of the Eu(3+)-3(NO3(-)) ion pairs involves incorporation of the "hard" metal complex into the core of "soft" aggregates. This seeds the formation of reverse micelles that draw the water and "free" amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod-shaped polynuclear Eu(III) -containing aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, containing high densities of O-donor ligands and anions, provide improved Eu(III) solvation environments that help drive interfacial transfer, as is reflected by the increasing Eu(III) partitioning ratios (oil/aqueous) despite the organic phase approaching saturation. For the first time, this multiscale approach links metal-ion coordination with nanoscale structure to reveal the free-energy balance that drives the phase transfer of neutral metal salts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jiajun; Wang, Liguang; Eng, Christopher

We present that irreversible electrochemical behavior and large voltage hysteresis are commonly observed in battery materials, in particular for materials reacting through conversion reaction, resulting in undesirable round-trip energy loss and low coulombic efficiency. Seeking solutions to these challenges relies on the understanding of the underlying mechanism and physical origins. Here, this study combines in operando 2D transmission X-ray microscopy with X-ray absorption near edge structure, 3D tomography, and galvanostatic intermittent titration techniques to uncover the conversion reaction in sodium–metal sulfide batteries, a promising high-energy battery system. This study shows a high irreversible electrochemistry process predominately occurs at first cycle,more » which can be largely linked to Na ion trapping during the first desodiation process and large interfacial ion mobility resistance. Subsequently, phase transformation evolution and electrochemical reaction show good reversibility at multiple discharge/charge cycles due to materials' microstructural change and equilibrium. The origin of large hysteresis between discharge and charge is investigated and it can be attributed to multiple factors including ion mobility resistance at the two-phase interface, intrinsic slow sodium ion diffusion kinetics, and irreversibility as well as ohmic voltage drop and overpotential. In conclusion, this study expects that such understandings will help pave the way for engineering design and optimization of materials microstructure for future-generation batteries.« less

Interfacial thermodynamics of water and six other liquid solvents.

PubMed

Pascal, Tod A; Goddard, William A

2014-06-05

We examine the thermodynamics of the liquid-vapor interface by direct calculation of the surface entropy, enthalpy, and free energy from extensive molecular dynamics simulations using the two-phase thermodynamics (2PT) method. Results for water, acetonitrile, cyclohexane, dimethyl sulfoxide, hexanol, N-methyl acetamide, and toluene are presented. We validate our approach by predicting the interfacial surface tensions (IFT--excess surface free energy per unit area) in excellent agreement with the mechanical calculations using Kirkwood-Buff theory. Additionally, we evaluate the temperature dependence of the IFT of water as described by the TIP4P/2005, SPC/Ew, TIP3P, and mW classical water models. We find that the TIP4P/2005 and SPC/Ew water models do a reasonable job of describing the interfacial thermodynamics; however, the TIP3P and mW are quite poor. We find that the underprediction of the experimental IFT at 298 K by these water models results from understructured surface molecules whose binding energies are too weak. Finally, we performed depth profiles of the interfacial thermodynamics which revealed long tails that extend far into what would be considered bulk from standard Gibbs theory. In fact, we find a nonmonotonic interfacial free energy profile for water, a unique feature that could have important consequences for the absorption of ions and other small molecules.

High On/Off Ratio Memristive Switching of Manganite/Cuprate Bilayer by Interfacial Magnetoelectricity

DOE PAGES

Shen, Xiao; Pennycook, Timothy J.; Hernandez-Martin, David; ...

2016-05-27

Memristive switching serves as the basis for a new generation of electronic devices. Conventional memristors are two-terminal devices in which the current is turned on and off by redistributing point defects, e.g., vacancies. Memristors based on alternative mechanisms have been explored, but achieving both high on/off ratio and low switching energy, as needed in applications, remains a challenge. This paper reports memristive switching in La 0.7Ca 0.3MnO 3/PrBa 2Cu 3O 7 bilayers with an on/off ratio greater than 103 and results of density functional theory calculations in terms of which it is concluded that the phenomenon is likely the resultmore » of a new type of interfacial magnetoelectricity. More specifically, this study shows that an external electric field induces subtle displacements of the interfacial Mn ions, which switches on/off an interfacial magnetic “dead layer”, resulting in memristive behavior for spin-polarized electron transport across the bilayer. The interfacial nature of the switching entails low energy cost, about of a tenth of atto Joule for writing/erasing a “bit”. To conclude, the results indicate new opportunities for manganite/cuprate systems and other transition metal oxide junctions in memristive applications.« less

Atomic Layer Deposition of Stable LiAlF4 Lithium Ion Conductive Interfacial Layer for Stable Cathode Cycling.

PubMed

Xie, Jin; Sendek, Austin D; Cubuk, Ekin D; Zhang, Xiaokun; Lu, Zhiyi; Gong, Yongji; Wu, Tong; Shi, Feifei; Liu, Wei; Reed, Evan J; Cui, Yi

2017-07-25

Modern lithium ion batteries are often desired to operate at a wide electrochemical window to maximize energy densities. While pushing the limit of cutoff potentials allows batteries to provide greater energy densities with enhanced specific capacities and higher voltage outputs, it raises key challenges with thermodynamic and kinetic stability in the battery. This is especially true for layered lithium transition-metal oxides, where capacities can improve but stabilities are compromised as wider electrochemical windows are applied. To overcome the above-mentioned challenges, we used atomic layer deposition to develop a LiAlF 4 solid thin film with robust stability and satisfactory ion conductivity, which is superior to commonly used LiF and AlF 3 . With a predicted stable electrochemical window of approximately 2.0 ± 0.9 to 5.7 ± 0.7 V vs Li + /Li for LiAlF 4 , excellent stability was achieved for high Ni content LiNi 0.8 Mn 0.1 Co 0.1 O 2 electrodes with LiAlF 4 interfacial layer at a wide electrochemical window of 2.75-4.50 V vs Li + /Li.

Effect of counterions on the shape, hydration, and degree of order at the interface of cationic micelles: the triflate case.

PubMed

Lima, Filipe S; Cuccovia, Iolanda M; Horinek, Dominik; Amaral, Lia Q; Riske, Karin A; Schreier, Shirley; Salinas, Roberto K; Bastos, Erick L; Pires, Paulo A R; Bozelli, José Carlos; Favaro, Denize C; Rodrigues, Ana Clara B; Dias, Luís Gustavo; El Seoud, Omar A; Chaimovich, Hernan

2013-04-02

Specific ion effects in surfactant solutions affect the properties of micelles. Dodecyltrimethylammonium chloride (DTAC), bromide (DTAB), and methanesulfonate (DTAMs) micelles are typically spherical, but some organic anions can induce shape or phase transitions in DTA(+) micelles. Above a defined concentration, sodium triflate (NaTf) induces a phase separation in dodecyltrimethylammonium triflate (DTATf) micelles, a phenomenon rarely observed in cationic micelles. This unexpected behavior of the DTATf/NaTf system suggests that DTATf aggregates have unusual properties. The structural properties of DTATf micelles were analyzed by time-resolved fluorescence quenching, small-angle X-ray scattering, nuclear magnetic resonance, and electron paramagnetic resonance and compared with those of DTAC, DTAB, and DTAMs micelles. Compared to the other micelle types, the DTATf micelles had a higher average number of monomers per aggregate, an uncommon disk-like shape, smaller interfacial hydration, and restricted monomer chain mobility. Molecular dynamic simulations supported these observations. Even small water-soluble salts can profoundly affect micellar properties; our data demonstrate that the -CF3 group in Tf(-) was directly responsible for the observed shape changes by decreasing interfacial hydration and increasing the degree of order of the surfactant chains in the DTATf micelles.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vissers, Daniel R.; Isheim, Dieter; Zhan, Chun

Lithium-ion batteries utilizing 5 V spinel material, LixMn1.5Ni0.5O4 have received considerable interest in recent years for their ability to deliver high energy and power densities. In this paper, we report an atomic scale analysis of the surface layer of a core–shell 5 V spinel structure where a small amount of the manganese lattice sites have been substituted with cobalt in the shell to reach a stoichiometry of LixMn1.18Ni0.55Co0.27O4. Our analyses include electrochemical analysis, atom probe tomography (APT) analysis, kinetic analysis of the interfacial reactions, and high resolution scanning transmission electron microscopy (HR-TEM) analysis. The APT analysis is performed on themore » material before and after long-term cycling at room temperature to provide insights into the atomic scale phenomena within the surface layer of the electrode material. Our APT data reveals a 25–30 nano-meter (nm) region which forms after cycling. From our analyses, we believe that the outer few nanometers of this region stabilizes the 5 V spinel within the chemical environment of the lithium-ion cell such that its structure is not compromised and thereby enables this material to cycle without significant capacity fading.« less

Water at surfaces with tunable surface chemistries

NASA Astrophysics Data System (ADS)

Sanders, Stephanie E.; Vanselous, Heather; Petersen, Poul B.

2018-03-01

Aqueous interfaces are ubiquitous in natural environments, spanning atmospheric, geological, oceanographic, and biological systems, as well as in technical applications, such as fuel cells and membrane filtration. Where liquid water terminates at a surface, an interfacial region is formed, which exhibits distinct properties from the bulk aqueous phase. The unique properties of water are governed by the hydrogen-bonded network. The chemical and physical properties of the surface dictate the boundary conditions of the bulk hydrogen-bonded network and thus the interfacial properties of the water and any molecules in that region. Understanding the properties of interfacial water requires systematically characterizing the structure and dynamics of interfacial water as a function of the surface chemistry. In this review, we focus on the use of experimental surface-specific spectroscopic methods to understand the properties of interfacial water as a function of surface chemistry. Investigations of the air-water interface, as well as efforts in tuning the properties of the air-water interface by adding solutes or surfactants, are briefly discussed. Buried aqueous interfaces can be accessed with careful selection of spectroscopic technique and sample configuration, further expanding the range of chemical environments that can be probed, including solid inorganic materials, polymers, and water immiscible liquids. Solid substrates can be finely tuned by functionalization with self-assembled monolayers, polymers, or biomolecules. These variables provide a platform for systematically tuning the chemical nature of the interface and examining the resulting water structure. Finally, time-resolved methods to probe the dynamics of interfacial water are briefly summarized before discussing the current status and future directions in studying the structure and dynamics of interfacial water.

A Spinel-integrated P2-type Layered Composite: High-rate Cathode for Sodium-ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jianming; Yan, Pengfei; Kan, Wang Hay

2016-01-14

Sodium-ion batteries (SIB) are being intensively investigated, owing to the natural abundance and low cost of Na resources. However, the SIBs still suffer from poor rate capability due to the large ionic radius of Na+ ion and the significant kinetic barrier to Na+-ion transport. Here, we present an Fd-3m spinel-integrated P2-type layered composite (P2 + Fd-3m) material as a high-rate cathode for SIBs. The P2 + Fd-3m composite material Na0.50Ni1/6Co1/6Mn2/3O2 shows significantly enhanced discharge capacity, energy density, and rate capability as compared to the pure P2-type counterpart. The composite delivers a high capacity of 85 mA h g-1 when dischargingmore » at a very high current density of 1500 mA g-1 (10C rate) between 2.0 and 4.5 V, validating it as a promising cathode candidate for high-power SIBs. The superior performance is ascribed to the improved kinetics in the presence of the integrated-spinel phase, which facilitates fast electron transport to coordinate with the timely Na+-ion insertion/extraction. The findings of this work also shed light on the importance of developing lattice doping, surface coating, and electrolyte additives to further improve the structural and interfacial stability of P2-type cathode materials and fully realize their practical applications in sodium-ion batteries.« less

Intermolecular network analysis of the liquid and vapor interfaces of pentane and water: microsolvation does not trend with interfacial properties.

PubMed

Ghadar, Yasaman; Clark, Aurora E

2014-06-28

Liquid:vapor and liquid:liquid interfaces exhibit complex organizational structure and dynamics at the molecular level. In the case of water and organic solvents, the hydrophobicity of the organic, its conformational flexibility, and compressibility, all influence interfacial properties. This work compares the interfacial tension, width, molecular conformations and orientations at the vapor and aqueous liquid interfaces of two solvents, n-pentane and neopentane, whose varying molecular shapes can lead to significantly different interfacial behavior. Particular emphasis has been dedicated toward understanding how the hydrogen bond network of water responds to the pentane relative to the vapor interface and the sensitivity of the network to the individual pentane isomer and system temperature. Interfacial microsolvation of the immiscible solvents has been examined using graph theoretical methods that quantify the structure and dynamics of microsolvated species (both H2O in C5H12 and C5H12 in H2O). At room temperature, interfacial water at the pentane phase boundary is found to have markedly different organization and dynamics than at the vapor interface (as indicated by the hydrogen bond distributions and hydrogen bond persistence in solution). While the mesoscale interfacial properties (e.g. interfacial tension) are sensitive to the specific pentane isomer, the distribution and persistence of microsolvated species at the interface is nearly identical for both systems, irrespective of temperature (between 273 K and 298 K). This has important implications for understanding how properties defined by the interfacial organization are related to the underlying solvation reactions that drive formation of the phase boundary.

Ultrastructural characterization of tooth-biomaterial interfaces prepared with broad and focused ion beams.

PubMed

Coutinho, E; Jarmar, T; Svahn, F; Neves, A A; Verlinden, B; Van Meerbeek, B; Engqvist, H

2009-11-01

Current available techniques for transmission electron microscopy (TEM) of tooth-biomaterial interfaces are mostly ineffective for brittle phases and impair integrated chemical and morphological characterization. The aims of this study were (1) to determine the applicability of new focused ion beam (FIB) and broad ion beam (BIB) techniques for TEM preparation of tooth-biomaterial interfaces; (2) to characterize the interfacial interaction with enamel and dentin of a conventional glass-ionomer (Chemfil Superior, DeTrey Dentsply, Germany), a 2-step self-etch (Clearfil SE, Kuraray, Japan) and a 3-step etch-and-rinse (OptiBond FL, Kerr, USA) adhesives; and (3) to characterize clinically relevant interfaces obtained from actual Class-I cavities. After bonding to freshly extracted human third molars, non-demineralized and non-stained sections were obtained using the FIB/BIB techniques and examined under TEM. The main structures generally disclosed in conventional ultramicrotomy samples were recognized in FIB/BIB-based ones. There were not any major differences between FIB and BIB concerning the resulting ultrastructural morphology. FIB/BIB-sections enabled to clearly resolve sub-micron hydroxyapatite crystals on top of hard tissues and the interface between matrix and filler in all materials, even at nano-scale. Some investigated interfaces disclosed areas with a distinct "fog" or "melted look", which is probably an artifact due to surface damage caused by the high-energy beam. Interfaces with enamel clearly disclosed the distinct "keyhole" shape of enamel rods sectioned at 90 degrees , delimited by a thin electron-lucent layer of inter-rod enamel. At regions where enamel crystals ran parallel with the interface, we observed a lack of interaction and some de-bonding along with interfacial void formation. The FIB/BIB methods are viable and reliable alternatives to conventional ultramicrotomy for preparation of thin sections of brittle and thus difficult to cut biomaterial-hard tissue interfaces. They disclose additional ultrastructural information about both substrates and are more suitable for advanced analytic procedures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ziying; Lee, Jungwoo Z.; Xin, Huolin L.

All-solid-state lithium-ion batteries have the potential to not only push the current limits of energy density by utilizing Li metal, but also improve safety by avoiding flammable organic electrolyte. However, understanding the role of solid electrolyte – electrode interfaces will be critical to improve performance. In this paper, we conducted long term cycling on commercially available lithium cobalt oxide (LCO)/lithium phosphorus oxynitride (LiPON)/lithium (Li) cells at elevated temperature to investigate the interfacial phenomena that lead to capacity decay. STEM-EELS analysis of samples revealed a previously unreported disordered layer between the LCO cathode and LiPON electrolyte. This electrochemically inactive layer grewmore » in thickness leading to loss of capacity and increase of interfacial resistance when cycled at 80 °C. Finally, the stabilization of this layer through interfacial engineering is crucial to improve the long term performance of thin-film batteries especially under thermal stress.« less

Modeling micelle formation and interfacial properties with iSAFT classical density functional theory

NASA Astrophysics Data System (ADS)

Wang, Le; Haghmoradi, Amin; Liu, Jinlu; Xi, Shun; Hirasaki, George J.; Miller, Clarence A.; Chapman, Walter G.

2017-03-01

Surfactants reduce the interfacial tension between phases, making them an important additive in a number of industrial and commercial applications from enhanced oil recovery to personal care products (e.g., shampoo and detergents). To help obtain a better understanding of the dependence of surfactant properties on molecular structure, a classical density functional theory, also known as interfacial statistical associating fluid theory, has been applied to study the effects of surfactant architecture on micelle formation and interfacial properties for model nonionic surfactant/water/oil systems. In this approach, hydrogen bonding is explicitly included. To minimize the free energy, the system minimizes interactions between hydrophobic components and hydrophilic components with water molecules hydrating the surfactant head group. The theory predicts micellar structure, effects of surfactant architecture on critical micelle concentration, aggregation number, and interfacial tension isotherm of surfactant/water systems in qualitative agreement with experimental data. Furthermore, this model is applied to study swollen micelles and reverse swollen micelles that are necessary to understand the formation of a middle-phase microemulsion.

Role of oxygen functional groups for structure and dynamics of interfacial water on low rank coal surface: a molecular dynamics simulation

NASA Astrophysics Data System (ADS)

You, Xiaofang; Wei, Hengbin; Zhu, Xianchang; Lyu, Xianjun; Li, Lin

2018-07-01

Molecular dynamics simulations were employed to study the effects of oxygen functional groups for structure and dynamics properties of interfacial water molecules on the subbituminous coal surface. Because of complex composition and structure, the graphite surface modified by hydroxyl, carboxyl and carbonyl groups was used to represent the surface model of subbituminous coal according to XPS results, and the composing proportion for hydroxyl, carbonyl and carboxyl is 25:3:5. The hydration energy with -386.28 kJ/mol means that the adsorption process between water and coal surface is spontaneous. Density profiles for oxygen atoms and hydrogen atoms indicate that the coal surface properties affect the structural and dynamic characteristics of the interfacial water molecules. The interfacial water exhibits much more ordering than bulk water. The results of radial distribution functions, mean square displacement and local self-diffusion coefficient for water molecule related to three oxygen moieties confirmed that the water molecules prefer to absorb with carboxylic groups, and adsorption of water molecules at the hydroxyl and carbonyl is similar.

Fabrication of single Ga-doped ZnS nanowires as high-gain photosensors by focused ion beam deposition

NASA Astrophysics Data System (ADS)

Yen, Shih-Hsiang; Hung, Yu-Chen; Yeh, Ping-Hung; Su, Ya-Wen; Wang, Chiu-Yen

2017-09-01

ZnS nanowires were synthesized via a vapor-liquid-solid mechanism and then fabricated into a single-nanowire field-effect transistor by focused ion beam (FIB) deposition. The field-effect electrical properties of the FIB-fabricated ZnS nanowire device, namely conductivity, mobility and hole concentration, were 9.13 Ω-1 cm-1, 13.14 cm2 V-1 s-1and 4.27 × 1018 cm-3, respectively. The photoresponse properties of the ZnS nanowires were studied and the current responsivity, current gain, response time and recovery time were 4.97 × 106 A W-1, 2.43 × 107, 9 s and 24 s, respectively. Temperature-dependent I-V measurements were used to analyze the interfacial barrier height between ZnS and the FIB-deposited Pt electrode. The results show that the interfacial barrier height is as low as 40 meV. The energy-dispersive spectrometer elemental line scan shows the influence of Ga ions on the ZnS nanowire surface on the FIB-deposited Pt contact electrodes. The results of temperature-dependent I-V measurements and the elemental line scan indicate that Ga ions were doped into the ZnS nanowire, reducing the barrier height between the FIB-deposited Pt electrodes and the single ZnS nanowire. The small barrier height results in the FIB-fabricated ZnS nanowire device acting as a high-gain photosensor.

Emerging applications of spark plasma sintering in all solid-state lithium-ion batteries and beyond

NASA Astrophysics Data System (ADS)

Zhu, Hongzheng; Liu, Jian

2018-07-01

Solid-state batteries have received increasing attention due to their high safety aspect and high energy and power densities. However, the development of solid-state batteries is hindered by inferior solid-solid interfaces between the solid-state electrolyte and electrode, which cause high interfacial resistance, reduced Li-ion and electron transfer rate, and limited battery performance. Recently, spark plasma sintering (SPS) is emerging as a promising technique for fabricating solid-state electrolyte and electrode pellets with clean and intimate solid-solid interfaces. During the SPS process, the unique reaction mechanism through the combination of current, pressure and high heating rate allow the formation of desirable solid-solid interfaces between active material particles. Herein, this work focuses on the overview of the application of SPS for fabricating solid-state electrolyte and electrode in all solid-state Li-ion batteries, and beyond, such as solid-state Li-S and Na-ion batteries. The correlations among SPS parameters, interfacial resistance, and electrochemical properties of solid-state electrolytes and electrodes are discussed for different material systems. In the end, we point out future opportunities and challenges associated with SPS application in the hot area of solid-state batteries. It is expected that this timely review will stimulate more fundamental and applied research in the development of solid-state batteries by SPS.

Improving the durability of the optical fiber sensor based on strain transfer analysis

NASA Astrophysics Data System (ADS)

Wang, Huaping; Jiang, Lizhong; Xiang, Ping

2018-05-01

To realize the reliable and long-term strain detection, the durability of optical fiber sensors has attracted more and more attention. The packaging technique has been considered as an effective method, which can enhance the survival ratios of optical fiber sensors to resist the harsh construction and service environment in civil engineering. To monitor the internal strain of structures, the embedded installation is adopted. Due to the different material properties between host material and the protective layer, the monitored structure embedded with sensors can be regarded as a typical model containing inclusions. Interfacial characteristic between the sensor and host material exists obviously, and the contacted interface is prone to debonding failure induced by the large interfacial shear stress. To recognize the local interfacial debonding damage and extend the effective life cycle of the embedded sensor, strain transfer analysis of a general three-layered sensing model is conducted to investigate the failure mechanism. The perturbation of the embedded sensor on the local strain field of host material is discussed. Based on the theoretical analysis, the distribution of the interfacial shear stress along the sensing length is characterized and adopted for the diagnosis of local interfacial debonding, and the sensitive parameters influencing the interfacial shear stress are also investigated. The research in this paper explores the interfacial debonding failure mechanism of embedded sensors based on the strain transfer analysis and provides theoretical basis for enhancing the interfacial bonding properties and improving the durability of embedded optical fiber sensors.

Bubble-Sheet-Like Interface Design with an Ultrastable Solid Electrolyte Layer for High-Performance Dual-Ion Batteries.

PubMed

Qin, Panpan; Wang, Meng; Li, Na; Zhu, Haili; Ding, Xuan; Tang, Yongbing

2017-05-01

In this work, a bubble-sheet-like hollow interface design on Al foil anode to improve the cycling stability and rate performance of aluminum anode based dual-ion battery is reported, in which, a carbon-coated hollow aluminum anode is used as both anode materials and current collector. This anode structure can guide the alloying position inside the hollow nanospheres, and also confine the alloy sizes within the hollow nanospheres, resulting in significantly restricted volumetric expansion and ultrastable solid electrolyte interface (SEI). As a result, the battery demonstrates an excellent long-term cycling stability within 1500 cycles with ≈99% capacity retention at 2 C. Moreover, this cell displays an energy density of 169 Wh kg -1 even at high power density of 2113 W kg -1 (10 C, charge and discharge within 6 min), which is much higher than most of conventional lithium ion batteries. The interfacial engineering strategy shown in this work to stabilize SEI layer and control the alloy forming position could be generalized to promote the research development of metal anodes based battery systems. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ion-size dependent electroosmosis of viscoelastic fluids in microfluidic channels with interfacial slip

NASA Astrophysics Data System (ADS)

Mukherjee, Siddhartha; Goswami, Prakash; Dhar, Jayabrata; Dasgupta, Sunando; Chakraborty, Suman

2017-07-01

We report a study on the ion-size dependent electroosmosis of viscoelastic fluids in microfluidic channels with interfacial slip. Here, we derive an analytical solution for the potential distribution in a parallel plate microchannel, where the effects of finite sized ionic species are taken into account by invoking the free energy formalism. Following this, a purely electroosmotic flow of a simplified Phan-Thien-Tanner (sPTT) fluid is considered. For the sPTT model, linear, quadratic, and exponential kernels are chosen for the stress coefficient function describing its viscoelastic nature across various ranges of Deborah number. The theoretical framework presented in our analysis has been successfully compared with experimental results available in the literature. We believe that the implications of the considered effects on the net volumetric throughput will not only provide a deeper theoretical insight to interpret the electrokinetic data in the presence of ionic species but also serve as a fundamental design tool for novel electrokinetically driven lab-on-a-chip biofluidic devices.

Minimizing analyte electrolysis in electrospray ionization mass spectrometry using a redox buffer coated emitter electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peintler-Krivan, Emese; Van Berkel, Gary J; Kertesz, Vilmos

2010-01-01

An emitter electrode with an electroactive poly(pyrrole) (PPy) polymer film coating was constructed for use in electrospray ionization mass spectrometry (ESI-MS). The PPy film acted as a surface-attached redox buffer limiting the interfacial potential of the emitter electrode. While extensive oxidation of selected analytes (reserpine and amodiaquine) was observed in positive ion mode ESI using a bare metal (gold) emitter electrode, the oxidation was suppressed for these same analytes when using the PPy-coated electrode. A semi-quantitative relationship between the rate of oxidation observed and the interfacial potential of the emitter electrode was shown. The redox buffer capacity, and therefore themore » lifetime of the redox buffering effect, correlated with the oxidation potential of the analyte and with the magnitude of the film charge capacity. Online reduction of the PPy polymer layer using negative ion mode ESI between analyte injections was shown to successfully restore the redox buffering capacity of the polymer film to its initial state.« less

Rational coating of Li7P3S11 solid electrolyte on MoS2 electrode for all-solid-state lithium ion batteries

NASA Astrophysics Data System (ADS)

Xu, R. C.; Wang, X. L.; Zhang, S. Z.; Xia, Y.; Xia, X. H.; Wu, J. B.; Tu, J. P.

2018-01-01

Large interfacial resistance between electrode and electrolyte limits the development of high-performance all-solid-state batteries. Herein we report a uniform coating of Li7P3S11 solid electrolyte on MoS2 to form a MoS2/Li7P3S11 composite electrode for all-solid-state lithium ion batteries. The as-synthesized Li7P3S11 processes a high ionic of 2.0 mS cm-1 at room temperature. Due to homogeneous union and reduced interfacial resistance, the assembled all-solid-state batteries with the MoS2/Li7P3S11 composite electrode exhibit higher reversible capacity of 547.1 mAh g-1 at 0.1 C and better cycling stability than the counterpart based on untreated MoS2. Our study provides a new reference for design/fabrication of advanced electrode materials for high-performance all-solid-state batteries.

Extracting elastic properties of an atomically thin interfacial layer by time-domain analysis of femtosecond acoustics

NASA Astrophysics Data System (ADS)

Chen, H.-Y.; Huang, Y.-R.; Shih, H.-Y.; Chen, M.-J.; Sheu, J.-K.; Sun, C.-K.

2017-11-01

Modern devices adopting denser designs and complex 3D structures have created much more interfaces than before, where atomically thin interfacial layers could form. However, fundamental information such as the elastic property of the interfacial layers is hard to measure. The elastic property of the interfacial layer is of great importance in both thermal management and nano-engineering of modern devices. Appropriate techniques to probe the elastic properties of interfacial layers as thin as only several atoms are thus critically needed. In this work, we demonstrated the feasibility of utilizing the time-resolved femtosecond acoustics technique to extract the elastic properties and mass density of a 1.85-nm-thick interfacial layer, with the aid of transmission electron microscopy. We believe that this femtosecond acoustics approach will provide a strategy to measure the absolute elastic properties of atomically thin interfacial layers.

Proton Transfer Dynamics at the Membrane/Water Interface: Dependence on the Fixed and Mobile pH Buffers, on the Size and Form of Membrane Particles, and on the Interfacial Potential Barrier

PubMed Central

Cherepanov, Dmitry A.; Junge, Wolfgang; Mulkidjanian, Armen Y.

2004-01-01

Crossing the membrane/water interface is an indispensable step in the transmembrane proton transfer. Elsewhere we have shown that the low dielectric permittivity of the surface water gives rise to a potential barrier for ions, so that the surface pH can deviate from that in the bulk water at steady operation of proton pumps. Here we addressed the retardation in the pulsed proton transfer across the interface as observed when light-triggered membrane proton pumps ejected or captured protons. By solving the system of diffusion equations we analyzed how the proton relaxation depends on the concentration of mobile pH buffers, on the surface buffer capacity, on the form and size of membrane particles, and on the height of the potential barrier. The fit of experimental data on proton relaxation in chromatophore vesicles from phototropic bacteria and in bacteriorhodopsin-containing membranes yielded estimates for the interfacial potential barrier for H+/OH− ions of ∼120 meV. We analyzed published data on the acceleration of proton equilibration by anionic pH buffers and found that the height of the interfacial barrier correlated with their electric charge ranging from 90 to 120 meV for the singly charged species to >360 meV for the tetra-charged pyranine. PMID:14747306

The effect of millisecond flash lamp annealing on electrical and structural properties of ZnO:Al/Si structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindberg, P. F.; Riise, H. N.; Vines, L.

2016-05-14

The effect of millisecond flash lamp annealing (FLA) on aluminum doped ZnO (AZO) films and their interface with Si have been studied. The AZO films were deposited by magnetron sputtering on Si (100) substrates. The electrical and structural properties of the film and AZO/Si structures were characterized by current–voltage, capacitance–voltage, and deep level transient spectroscopy measurements, X-ray diffraction, and secondary ion mass spectrometry. The resistivity of the AZO film is reduced to a close to state-of-the-art value of 2 × 10{sup −4} Ω cm after FLA for 3 ms with an average energy density of 29 J/cm{sup 2}. In addition, most of the interfacial defects energymore » levels are simultaneously annealed out, except for one persisting shallow level, tentatively assigned to the vacancy-oxygen complex in Si, which was not affected by FLA. Subsequent to the FLA, the samples were treated in N{sub 2} or forming gas (FG) (N{sub 2}/H{sub 2}, 90/10%{sub mole}) ambient at 200–500 °C. The latter samples maintained the low resistivity achieved after the FLA, but not the former ones. The interfacial defect level persisting after the FLA is removed by the FG treatment, concurrently as another level emerges at ∼0.18 eV below the conduction band. The electrical data of the AZO films are discussed in term of point defects controlling the resistivity, and it is argued that the FLA promotes formation of electrically neutral clusters of Zink vacancies (V{sub Zn}'s) rather than passivating/compensating complexes between the Al donors and V{sub Zn}'s.« less

Wetting, meniscus structure, and capillary interactions of microspheres bound to a cylindrical liquid interface.

PubMed

Kim, Paul Y; Dinsmore, Anthony D; Hoagland, David A; Russell, Thomas P

2018-03-14

Wetting, meniscus structure, and capillary interactions for polystyrene microspheres deposited on constant curvature cylindrical liquid interfaces, constructed from nonvolatile ionic or oligomeric liquids, were studied by optical interferometry and optical microscopy. The liquid interface curvature resulted from the preferential wetting of finite width lines patterned onto planar silicon substrates. Key variables included sphere diameter, nominal (or average) contact angle, and deviatoric interfacial curvature. Menisci adopted the quadrupolar symmetry anticipated by theory, with interfacial deformation closely following predicted dependences on sphere diameter and nominal contact angle. Unexpectedly, the contact angle was not constant locally around the contact line, the nominal contact angle varied among seemingly identical spheres, and the maximum interface deviation did not follow the predicted dependence on deviatoric interfacial curvature. Instead, this deviation was up to an order-of-magnitude larger than predicted. Trajectories of neighboring microspheres visually manifested quadrupole-quadrupole interactions, eventually producing square sphere packings that foreshadow interfacial assembly as a potential route to hierarchical 2D particle structures.

Structure from Dynamics: Vibrational Dynamics of Interfacial Water as a Probe of Aqueous Heterogeneity

PubMed Central

2018-01-01

The structural heterogeneity of water at various interfaces can be revealed by time-resolved sum-frequency generation spectroscopy. The vibrational dynamics of the O–H stretch vibration of interfacial water can reflect structural variations. Specifically, the vibrational lifetime is typically found to increase with increasing frequency of the O–H stretch vibration, which can report on the hydrogen-bonding heterogeneity of water. We compare and contrast vibrational dynamics of water in contact with various surfaces, including vapor, biomolecules, and solid interfaces. The results reveal that variations in the vibrational lifetime with vibrational frequency are very typical, and can frequently be accounted for by the bulk-like heterogeneous response of interfacial water. Specific interfaces exist, however, for which the behavior is less straightforward. These insights into the heterogeneity of interfacial water thus obtained contribute to a better understanding of complex phenomena taking place at aqueous interfaces, such as photocatalytic reactions and protein folding. PMID:29490138

Atomic-scale mapping of electronic structures across heterointerfaces by cross-sectional scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Chiu, Ya-Ping; Huang, Bo-Chao; Shih, Min-Chuan; Huang, Po-Cheng; Chen, Chun-Wei

2015-09-01

Interfacial science has received much attention recently based on the development of state-of-the-art analytical tools that can create and manipulate the charge, spin, orbital, and lattice degrees of freedom at interfaces. Motivated by the importance of nanoscale interfacial science that governs device operation, we present a technique to probe the electronic characteristics of heterointerfaces with atomic resolution. In this work, the interfacial characteristics of heteroepitaxial structures are investigated and the fundamental mechanisms that pertain in these systems are elucidated through cross-sectional scanning tunneling microscopy (XSTM). The XSTM technique is employed here to directly observe epitaxial interfacial structures and probe local electronic properties with atomic-level capability. Scanning tunneling microscopy and spectroscopy experiments with atomic precision provide insight into the origin and spatial distribution of electronic properties across heterointerfaces. The first part of this report provides a brief description of the cleavage technique and spectroscopy analysis in XSTM measurements. The second part addresses interfacial electronic structures of several model heterostructures in current condensed matter research using XSTM. Topics to be discussed include high-κ‘s/III-V’s semiconductors, polymer heterojunctions, and complex oxide heterostructures, which are all material systems whose investigation using this technique is expected to benefit the research community. Finally, practical aspects and perspectives of using XSTM in interface science are presented.

Effects of Interfacial Fluorination on Performance Enhancement of High-k-Based Charge Trap Flash Memory

NASA Astrophysics Data System (ADS)

Wang, Chenjie; Huo, Zongliang; Liu, Ziyu; Liu, Yu; Cui, Yanxiang; Wang, Yumei; Li, Fanghua; Liu, Ming

2013-07-01

The effects of interfacial fluorination on the metal/Al2O3/HfO2/SiO2/Si (MAHOS) memory structure have been investigated. By comparing MAHOS memories with and without interfacial fluorination, it was identified that the deterioration of the performance and reliability of MAHOS memories is mainly due to the formation of an interfacial layer that generates excess oxygen vacancies at the interface. Interfacial fluorination suppresses the growth of the interfacial layer, which is confirmed by X-ray photoelectron spectroscopy depth profile analysis, increases enhanced program/erase efficiency, and improves data retention characteristics. Moreover, it was observed that fluorination at the SiO-HfO interface achieves a more effective performance enhancement than that at the HfO-AlO interface.

The interfacial character of antibody paratopes: analysis of antibody-antigen structures.

PubMed

Nguyen, Minh N; Pradhan, Mohan R; Verma, Chandra; Zhong, Pingyu

2017-10-01

In this study, computational methods are applied to investigate the general properties of antigen engaging residues of a paratope from a non-redundant dataset of 403 antibody-antigen complexes to dissect the contribution of hydrogen bonds, hydrophobic, van der Waals contacts and ionic interactions, as well as role of water molecules in the antigen-antibody interface. Consistent with previous reports using smaller datasets, we found that Tyr, Trp, Ser, Asn, Asp, Thr, Arg, Gly, His contribute substantially to the interactions between antibody and antigen. Furthermore, antibody-antigen interactions can be mediated by interfacial waters. However, there is no reported comprehensive analysis for a large number of structured waters that engage in higher ordered structures at the antibody-antigen interface. From our dataset, we have found the presence of interfacial waters in 242 complexes. We present evidence that suggests a compelling role of these interfacial waters in interactions of antibodies with a range of antigens differing in shape complementarity. Finally, we carry out 296 835 pairwise 3D structure comparisons of 771 structures of contact residues of antibodies with their interfacial water molecules from our dataset using CLICK method. A heuristic clustering algorithm is used to obtain unique structural similarities, and found to separate into 368 different clusters. These clusters are used to identify structural motifs of contact residues of antibodies for epitope binding. This clustering database of contact residues is freely accessible at http://mspc.bii.a-star.edu.sg/minhn/pclick.html. minhn@bii.a-star.edu.sg, chandra@bii.a-star.edu.sg or zhong_pingyu@immunol.a-star.edu.sg. Supplementary data are available at Bioinformatics online. © The Author (2017). Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Structure and functions of water-membrane interfaces and their role in proto-biological evolution

NASA Technical Reports Server (NTRS)

Pohorille, A.; Wilson, M.; Macelroy, R. D.

1991-01-01

Among the most important developments in proto-biological evolution was the emergence of membrane-like structures. These are formed by spontaneous association of relatively simple amphiphilic molecules that would have been readily available in the primordial environment. The resulting interfacial regions between water and nonpolar interior of the membrane have several properties which made them uniquely suitable for promoting subsequent evolution. They can (1) selectively attract organic material and mediate its transport, (2) serve as simple catalysts for chemical reactions, and (3) promote the formation of trans-membrane electrical and chemical gradients which could provide energy sources for proto-cells. Understanding the structure of interfaces, their interactions with organic molecules and molecular mechanisms of their functions is an essential step to understanding proto-biological evolution. In our computer simulation studies, we showed that the structure of water at interfaces with nonpolar media is significantly different from that in the bulk. In particular, the average surface dipole density points from the vapor to the liquid. As a result, negative ions can approach the interface more easily than positive ions. Amphiphilic molecules composed of hydrocarbon conjugated rings and polar substituents (e.g., phenol) assume at the interface rigid orientations in which polar groups are buried in water while hydrocarbon parts are located in the nonpolar environment. These orientational differences are of special interest in connection with the ability of some of these molecules to efficiently absorb photons. Flexible molecules with polar substituents often adopt at interfaces conformations different from those in the bulk aquaeous solution and in the gas phase. As a result, in many instances both specificity and kinetics of chemical reactions in which these molecules can participate is modified by the presence of surfaces. Of special interest is the mechanism by which polar molecules are transferred across interface between water and a nonpolar medium. Our recent study showed that simple ionophores bind ions by the same mechanisms as ion channels and carriers from modern cells.

Studies on the structural, optical and dielectric properties of samarium coordinated with salicylic acid single crystal

NASA Astrophysics Data System (ADS)

Singh, Harjinder; Slathia, Goldy; Gupta, Rashmi; Bamzai, K. K.

2018-04-01

Samarium coordinated with salicylic acid was successfully grown as a single crystal by low temperature solution technique using mixed solvent of methanol and water in equal ratio. Structural characterization was carried out by single crystal X-ray diffraction analysis and it crystallizes in centrosymmetric space group P121/c1. FTIR and UV-Vis-NIR spectroscopy confirmed the compound formation and help to determine the mode of binding of the ligand to the rare earth-metal ion. Dielectric constant and dielectric loss have been measured over the frequency range 100 Hz - 30MHz. The decrease in dielectric constant with increases in frequency is due to the transition from interfacial polarization to dipolar polarization. The small value of dielectric constant at higher frequency ensures that the crystal is good candidate for NLO devices. Dielectric loss represents the resistive nature of the material.

Hollow Few-Layer Graphene-Based Structures from Parafilm Waste for Flexible Transparent Supercapacitors and Oil Spill Cleanup.

PubMed

Nguyen, Duc Dung; Hsieh, Ping-Yen; Tsai, Meng-Ting; Lee, Chi-Young; Tai, Nyan-Hwa; To, Bao Dong; Vu, Duc Tu; Hsu, Chia Chen

2017-11-22

We report a versatile strategy to exploit parafilm waste as a carbon precursor for fabrication of freestanding, hollow few-layer graphene fiber mesh (HFGM) structures without use of any gaseous carriers/promoters via an annealing route. The freestanding HFGMs possess good mechanical flexibility, tailorable transparency, and high electrical conductivity, consequently qualifying them as promising electrochemical electrodes. Because of the hollow spaces, electrolyte ions can easily access into and contact with interior surfaces of the graphene fibers, accordingly increasing electrode/electrolyte interfacial area. As expected, solid-state supercapacitors based on the HFGMs exhibit a considerable enhancement in specific capacitance (20-30 fold) as compared to those employing chemical vapor deposition compact graphene films. Moreover, the parafilm waste is found to be beneficial for one-step fabrication of nanocarbon/few-layer graphene composite meshes with superior electrochemical performance, outstanding superhydrophobic property, good self-cleaning ability, and great promise for oil spill cleanup.

Investigation of energy band alignments and interfacial properties of rutile NMO2/TiO2 (NM = Ru, Rh, Os, and Ir) by first-principles calculations.

PubMed

Yang, Chen; Zhao, Zong-Yan

2017-11-08

In the field of photocatalysis, constructing hetero-structures is an efficient strategy to improve quantum efficiency. However, a lattice mismatch often induces unfavorable interfacial states that can act as recombination centers for photo-generated electron-hole pairs. If the hetero-structure's components have the same crystal structure, this disadvantage can be easily avoided. Conversely, in the process of loading a noble metal co-catalyst onto the TiO 2 surface, a transition layer of noble metal oxides is often formed between the TiO 2 layer and the noble metal layer. In this article, interfacial properties of hetero-structures composed of a noble metal dioxide and TiO 2 with a rutile crystal structure have been systematically investigated using first-principles calculations. In particular, the Schottky barrier height, band bending, and energy band alignments are studied to provide evidence for practical applications. In all cases, no interfacial states exist in the forbidden band of TiO 2 , and the interfacial formation energy is very small. A strong internal electric field generated by interfacial electron transfer leads to an efficient separation of photo-generated carriers and band bending. Because of the differences in the atomic properties of the components, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures demonstrate band dividing, while RhO 2 /TiO 2 and IrO 2 /TiO 2 hetero-structures have a pseudo-gap near the Fermi energy level. Furthermore, NMO 2 /TiO 2 hetero-structures show upward band bending. Conversely, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures present a relatively strong infrared light absorption, while RhO 2 /TiO 2 and IrO 2 /TiO 2 hetero-structures show an obvious absorption edge in the visible light region. Overall, considering all aspects of their properties, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures are more suitable than others for improving the photocatalytic performance of TiO 2 . These findings will provide useful information for understanding the role and effects of a noble metal dioxide as a transition layer between a noble metal co-catalyst and a TiO 2 photocatalyst.

Topology-generating interfacial pattern formation during liquid metal dealloying

DOE PAGES

Geslin, Pierre -Antoine; McCue, Ian; Gaskey, Bernard; ...

2015-11-19

Liquid metal dealloying has emerged as a novel technique to produce topologically complex nanoporous and nanocomposite structures with ultra-high interfacial area and other unique properties relevant for diverse material applications. This process is empirically known to require the selective dissolution of one element of a multicomponent solid alloy into a liquid metal to obtain desirable structures. However, how structures form is not known. Here we demonstrate, using mesoscale phase-field modelling and experiments, that nano/microstructural pattern formation during dealloying results from the interplay of (i) interfacial spinodal decomposition, forming compositional domain structures enriched in the immiscible element, and (ii) diffusion-coupled growthmore » of the enriched solid phase and the liquid phase into the alloy. We highlight how those two basic mechanisms interact to yield a rich variety of topologically disconnected and connected structures. Furthermore, we deduce scaling laws governing microstructural length scales and dealloying kinetics.« less

Topology-generating interfacial pattern formation during liquid metal dealloying.

PubMed

Geslin, Pierre-Antoine; McCue, Ian; Gaskey, Bernard; Erlebacher, Jonah; Karma, Alain

2015-11-19

Liquid metal dealloying has emerged as a novel technique to produce topologically complex nanoporous and nanocomposite structures with ultra-high interfacial area and other unique properties relevant for diverse material applications. This process is empirically known to require the selective dissolution of one element of a multicomponent solid alloy into a liquid metal to obtain desirable structures. However, how structures form is not known. Here we demonstrate, using mesoscale phase-field modelling and experiments, that nano/microstructural pattern formation during dealloying results from the interplay of (i) interfacial spinodal decomposition, forming compositional domain structures enriched in the immiscible element, and (ii) diffusion-coupled growth of the enriched solid phase and the liquid phase into the alloy. We highlight how those two basic mechanisms interact to yield a rich variety of topologically disconnected and connected structures. Moreover, we deduce scaling laws governing microstructural length scales and dealloying kinetics.

Effect of interfacial oxide layers on the current-voltage characteristics of Al-Si contacts

NASA Technical Reports Server (NTRS)

Porter, W. A.; Parker, D. L.

1976-01-01

Aluminum-silicon contacts with very thin interfacial oxide layers and various surface impurity concentrations are studied for both n and p-type silicon. To determine the surface impurity concentrations on p(+)-p and n(+)-n structures, a modified C-V technique was utilized. Effects of interfacial oxide layers and surface impurity concentrations on current-voltage characteristics are discussed based on the energy band diagrams from the conductance-voltage plots. The interfacial oxide and aluminum layer causes image contrasts on X-ray topographs.

Mesoscopic modeling of structural and thermodynamic properties of fluids confined by rough surfaces.

PubMed

Terrón-Mejía, Ketzasmin A; López-Rendón, Roberto; Gama Goicochea, Armando

2015-10-21

The interfacial and structural properties of fluids confined by surfaces of different geometries are studied at the mesoscopic scale using dissipative particle dynamics simulations in the grand canonical ensemble. The structure of the surfaces is modeled by a simple function, which allows us to simulate readily different types of surfaces through the choice of three parameters only. The fluids we have modeled are confined either by two smooth surfaces or by symmetrically and asymmetrically structured walls. We calculate structural and thermodynamic properties such as the density, temperature and pressure profiles, as well as the interfacial tension profiles for each case and find that a structural order-disorder phase transition occurs as the degree of surface roughness increases. However, the magnitude of the interfacial tension is insensitive to the structuring of the surfaces and depends solely on the magnitude of the solid-fluid interaction. These results are important for modern nanotechnology applications, such as in the enhanced recovery of oil, and in the design of porous materials with specifically tailored properties.

Hydrogen bonded structure, polarity, molecular motion and frequency fluctuations at liquid-vapor interface of a water-methanol mixture: an ab initio molecular dynamics study.

PubMed

Choudhuri, Jyoti Roy; Chandra, Amalendu

2014-10-07

We have performed ab initio molecular dynamics simulations of a liquid-vapor interfacial system consisting of a mixture of water and methanol molecules. Detailed results are obtained for the structural and dynamical properties of the bulk and interfacial regions of the mixture. Among structural properties, we have looked at the inhomogeneous density profiles of water and methanol molecules, hydrogen bond distributions and also the orientational profiles of bulk and interfacial molecules. The methanol molecules are found to have a higher propensity to be at the interface than water molecules. It is found that the interfacial molecules show preference for specific orientations so as to form water-methanol hydrogen bonds at the interface with the hydrophobic methyl group pointing towards the vapor side. It is also found that for both types of molecules, the dipole moment decreases at the interface. It is also found that the local electric field of water influences the dipole moment of methanol molecules. Among the dynamical properties, we have calculated the diffusion, orientational relaxation, hydrogen bond dynamics, and vibrational frequency fluctuations in bulk and interfacial regions. It is found that the diffusion and orientation relaxation of the interfacial molecules are faster than those of the bulk. However, the hydrogen bond lifetimes are longer at the interface which can be correlated with the time scales found from the decay of frequency time correlations. The slower hydrogen bond dynamics for the interfacial molecules with respect to bulk can be attributed to diminished cooperative effects at the interface due to reduced density and number of hydrogen bonds.

Controllable synthesis of MnO2/polyaniline nanocomposite and its electrochemical capacitive property

PubMed Central

2013-01-01

Polyaniline (PANI) and MnO2/PANI composites are simply fabricated by one-step interfacial polymerization. The morphologies and components of MnO2/PANI composites are modulated by changing the pH of the solution. Formation procedure and capacitive property of the products are investigated by XRD, FTIR, TEM, and electrochemical techniques. We demonstrate that MnO2 as an intermedia material plays a key role in the formation of sample structures. The MnO2/PANI composites exhibit good cycling stability as well as a high capacitance close to 207 F g−1. Samples fabricated with the facile one-step method are also expected to be adopted in other field such as catalysis, lithium ion battery, and biosensor. PMID:23594724

Controllable synthesis of MnO2/polyaniline nanocomposite and its electrochemical capacitive property

NASA Astrophysics Data System (ADS)

Meng, Fanhui; Yan, Xiuling; Zhu, Ye; Si, Pengchao

2013-04-01

Polyaniline (PANI) and MnO2/PANI composites are simply fabricated by one-step interfacial polymerization. The morphologies and components of MnO2/PANI composites are modulated by changing the pH of the solution. Formation procedure and capacitive property of the products are investigated by XRD, FTIR, TEM, and electrochemical techniques. We demonstrate that MnO2 as an intermedia material plays a key role in the formation of sample structures. The MnO2/PANI composites exhibit good cycling stability as well as a high capacitance close to 207 F g-1. Samples fabricated with the facile one-step method are also expected to be adopted in other field such as catalysis, lithium ion battery, and biosensor.

Dynamic nanoplatforms in biosensor and membrane constitutional systems.

PubMed

Mahon, Eugene; Aastrup, Teodor; Barboiu, Mihail

2012-01-01

Molecular recognition in biological systems occurs mainly at interfacial environments such as membrane surfaces, enzyme active sites, or the interior of the DNA double helix. At the cell membrane surface, carbohydrate-protein recognition principles apply to a range of specific non-covalent interactions including immune response, cell proliferation, adhesion and death, cell-cell interaction and communication. Protein-protein recognition meanwhile accounts for signalling processes and ion channel structure. In this chapter we aim to describe such constitutional dynamic interfaces for biosensing and membrane transport applications. Constitutionally adaptive interfaces may mimic the recognition capabilities intrinsic to natural recognition processes. We present some recent examples of 2D and 3D constructed sensors and membranes of this type and describe their sensing and transport capabilities.

The electrode/ionic liquid interface: electric double layer and metal electrodeposition.

PubMed

Su, Yu-Zhuan; Fu, Yong-Chun; Wei, Yi-Min; Yan, Jia-Wei; Mao, Bing-Wei

2010-09-10

The last decade has witnessed remarkable advances in interfacial electrochemistry in room-temperature ionic liquids. Although the wide electrochemical window of ionic liquids is of primary concern in this new type of solvent for electrochemistry, the unusual bulk and interfacial properties brought about by the intrinsic strong interactions in the ionic liquid system also substantially influence the structure and processes at electrode/ionic liquid interfaces. Theoretical modeling and experimental characterizations have been indispensable in reaching a microscopic understanding of electrode/ionic liquid interfaces and in elucidating the physics behind new phenomena in ionic liquids. This Minireview describes the status of some aspects of interfacial electrochemistry in ionic liquids. Emphasis is placed on high-resolution and molecular-level characterization by scanning tunneling microscopy and vibrational spectroscopies of interfacial structures, and the initial stage of metal electrodeposition with application in surface nanostructuring.

Observation of a Rare Earth Ion–Extractant Complex Arrested at the Oil–Water Interface During Solvent Extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bu, Wei; Yu, Hao; Luo, Guangming

2014-09-11

Selective extraction of metal ions from a complex aqueous mixture into an organic phase is used to separate toxic or radioactive metals from polluted environments and nuclear waste, as well as to produce industrially relevant metals, such as rare earth ions. Selectivity arises from the choice of an extractant amphiphile, dissolved in the organic phase, which interacts preferentially with the target metal ion. The extractant-mediated process of ion transport from an aqueous to an organic phase takes place at the aqueous–organic interface; nevertheless, little is known about the molecular mechanism of this process despite its importance. Although state-of-the-art X-ray scatteringmore » is uniquely capable of probing molecular ordering at a liquid–liquid interface with subnanometer spatial resolution, utilizing this capability to investigate interfacial dynamical processes of short temporal duration remains a challenge. We show that a temperature-driven adsorption transition can be used to turn the extraction on and off by controlling adsorption and desorption of extractants at the oil–water interface. Lowering the temperature through this transition immobilizes a supramolecular ion–extractant complex at the interface during the extraction of rare earth erbium ions. Under the conditions of these experiments, the ion–extractant complexes condense into a two-dimensional inverted bilayer, which is characterized on the molecular scale with synchrotron X-ray reflectivity and fluorescence measurements. Raising the temperature above the transition leads to Er ion extraction as a result of desorption of ion–extractant complexes from the interface into the bulk organic phase. XAFS measurements of the ion–extractant complexes in the bulk organic phase demonstrate that they are similar to the interfacial complexes.« less

Interfacial Structures of Trihexyltetradecylphosphonium-bis(mandelato)borate Ionic Liquid Confined between Gold Electrodes.

PubMed

Wang, Yong-Lei; Golets, Mikhail; Li, Bin; Sarman, Sten; Laaksonen, Aatto

2017-02-08

Atomistic molecular dynamics simulations have been performed to study microscopic the interfacial ionic structures, molecular arrangements, and orientational preferences of trihexyltetradecylphosphonium-bis(mandelato)borate ([P 6,6,6,14 ][BMB]) ionic liquid confined between neutral and charged gold electrodes. It was found that both [P 6,6,6,14 ] cations and [BMB] anions are coabsorbed onto neutral electrodes at different temperatures. The hexyl and tetradecyl chains in [P 6,6,6,14 ] cations lie preferentially flat on neutral electrodes. The oxalato and phenyl rings in [BMB] anions are characterized by alternative parallel-perpendicular orientations in the mixed innermost ionic layer adjacent to neutral electrodes. An increase in temperature has a marginal effect on the interfacial ionic structures and molecular orientations of [P 6,6,6,14 ][BMB] ionic species in a confined environment. Electrifying gold electrodes leads to peculiar changes in the interfacial ionic structures and molecular orientational arrangements of [P 6,6,6,14 ] cations and [BMB] anions in negatively and positively charged gold electrodes, respectively. As surface charge density increases (but lower than 20 μC/cm 2 ), the layer thickness of the mixed innermost interfacial layer gradually increases due to a consecutive accumulation of [P 6,6,6,14 ] cations and [BMB] anions at negatively and positively charged electrodes, respectively, before the formation of distinct cationic and anionic innermost layers. Meanwhile, the molecular orientations of two oxalato rings in the same [BMB] anions change gradually from a parallel-perpendicular feature to being partially characterized by a tilted arrangement at an angle of 45° from the electrodes and finally to a dominant parallel coordination pattern along positively charged electrodes. Distinctive interfacial distribution patterns are also observed accordingly for phenyl rings that are directly connected to neighboring oxalato rings in [BMB] anions.

High-discharge-rate lithium ion battery

DOEpatents

Liu, Gao; Battaglia, Vincent S; Zheng, Honghe

2014-04-22

The present invention provides for a lithium ion battery and process for creating such, comprising higher binder to carbon conductor ratios than presently used in the industry. The battery is characterized by much lower interfacial resistances at the anode and cathode as a result of initially mixing a carbon conductor with a binder, then with the active material. Further improvements in cycleability can also be realized by first mixing the carbon conductor with the active material first and then adding the binder.

Surface and interfacial chemistry of high-k dielectric and interconnect materials on silicon

NASA Astrophysics Data System (ADS)

Kirsch, Paul Daniel

Surfaces and interfaces play a critical role in the manufacture and function of silicon based integrated circuits. It is therefore reasonable to study the chemistries at these surfaces and interfaces to improve existing processes and to develop new ones. Model barium strontium titanate high-k dielectric systems have been deposited on ultrathin silicon oxynitride in ultrahigh vacuum. The resulting nanostructures are characterized with secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). An interfacial reaction between Ba and Sr atoms and SiOxNy was found to create silicates, BaSixOy or SrSi xOy. Inclusion of N in the interfacial oxide decreased silicate formation in both Ba and Sr systems. Furthermore, inclusion of N in the interfacial oxide decreased the penetration of Ba and Sr containing species, such as silicides and silicates. Sputter deposited HfO2 was studied on nitrided and unnitrided Si(100) surfaces. XPS and SIMS were used to verify the presence of interfacial HfSixOy and estimate its relative amount on both nitrided and unnitrided samples. More HfSixOy formed without the SiNx interfacial layer. These interfacial chemistry results are then used to explain the electrical measurements obtained from metal oxide semiconductor (MOS) capacitors. MOS capacitors with interfacial SiNx exhibit reduced leakage current and increased capacitance. Lastly, surface science techniques were used to develop a processing technique for reducing thin films of copper (II) and copper (I) oxide to copper. Deuterium atoms (D*) and methyl radicals (CH3*) were shown to reduce Cu 2+ and/or Cu1+ to Cu0 within 30 min at a surface temperature of 400 K under a flux of 1 x 1015 atoms/cm2s. Temperature programmed desorption experiments suggest that oxygen leaves the surface as D2O and CO2 for the D* and CH3* treated surfaces, respectively.

Rate theory of ion pairing at the water liquid-vapor interface: A case of sodium iodide.

PubMed

Dang, Liem X; Schenter, Gregory K

2018-06-14

Studies on ion pairing at interfaces have been intensified recently because of their importance in many chemical reactive phenomena, such as ion-ion interactions that are affected by interfaces and their influence on kinetic processes. In this study, we performed simulations to examine the thermodynamics and kinetics of small polarizable sodium iodide ions in the bulk and near the water liquid-vapor interface. Using classical transition state theory, we calculated the dissociation rates and corrected them with transmission coefficients obtained from the reactive flux formalism and Grote-Hynes theory. Our results show that in addition to affecting the free energy of ions in solution, the interfacial environments significantly influence the kinetics of ion pairing. The results on the relaxation time obtained using the reactive flux formalism and Grote-Hynes theory present an unequivocal picture that the interface suppresses ion dissociation. The effects of the use of molecular models on the ion interactions as well as the ion-pair configurations at the interface are also quantified and discussed.

Rate theory of ion pairing at the water liquid-vapor interface: A case of sodium iodide

NASA Astrophysics Data System (ADS)

Dang, Liem X.; Schenter, Gregory K.

2018-06-01

Studies on ion pairing at interfaces have been intensified recently because of their importance in many chemical reactive phenomena, such as ion-ion interactions that are affected by interfaces and their influence on kinetic processes. In this study, we performed simulations to examine the thermodynamics and kinetics of small polarizable sodium iodide ions in the bulk and near the water liquid-vapor interface. Using classical transition state theory, we calculated the dissociation rates and corrected them with transmission coefficients obtained from the reactive flux formalism and Grote-Hynes theory. Our results show that in addition to affecting the free energy of ions in solution, the interfacial environments significantly influence the kinetics of ion pairing. The results on the relaxation time obtained using the reactive flux formalism and Grote-Hynes theory present an unequivocal picture that the interface suppresses ion dissociation. The effects of the use of molecular models on the ion interactions as well as the ion-pair configurations at the interface are also quantified and discussed.

Effect of demulsifier partitioning on the destabilization of water-in-oil emulsions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Y.H.; Wasan, D.T.

1996-04-01

The factors affecting the demulsification and interfacial behavior of water-in-oil emulsions in the presence of oil-soluble demulsifiers were investigated. Using both model water-in-oil and water-in-crude oil emulsion systems with demulsifiers with different chemical structures, the effects of demulsifier partitioning on the interfacial and film rheological properties were studied. The experimental results were compared and related with the demulsifier performance. There is a one-to-one correlation between the performance of demulsifier and the interfacial activity of the partitioned demulsifier; the partitioned demulsifier components exhibit an increase in static and dynamic interfacial activity, low dynamic interfacial and film tension, and a low filmmore » dilational modulus with a high adsorption rate - low interfacial tension gradient (Marangoni-Gibbs stabilizing effect) and have excellent demulsification performance.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.

Here, the role of thin-film interfaces in the near-ultraviolet (near-UV) absorption and pulsed laser-induced damage was studied for ion-beam-sputtered and electron-beam-evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and anmore » E-field peak and average intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-UV, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the codeposition of HfO 2 and SiO 2 materials.« less

Interfacial behavior of polymer electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kerr, John; Kerr, John B.; Han, Yong Bong

2003-06-03

Evidence is presented concerning the effect of surfaces on the segmental motion of PEO-based polymer electrolytes in lithium batteries. For dry systems with no moisture the effect of surfaces of nano-particle fillers is to inhibit the segmental motion and to reduce the lithium ion transport. These effects also occur at the surfaces in composite electrodes that contain considerable quantities of carbon black nano-particles for electronic connection. The problem of reduced polymer mobility is compounded by the generation of salt concentration gradients within the composite electrode. Highly concentrated polymer electrolytes have reduced transport properties due to the increased ionic cross-linking. Combinedmore » with the interfacial interactions this leads to the generation of low mobility electrolyte layers within the electrode and to loss of capacity and power capability. It is shown that even with planar lithium metal electrodes the concentration gradients can significantly impact the interfacial impedance. The interfacial impedance of lithium/PEO-LiTFSI cells varies depending upon the time elapsed since current was turned off after polarization. The behavior is consistent with relaxation of the salt concentration gradients and indicates that a portion of the interfacial impedance usually attributed to the SEI layer is due to concentrated salt solutions next to the electrode surfaces that are very resistive. These resistive layers may undergo actual phase changes in a non-uniform manner and the possible role of the reduced mobility polymer layers in dendrite initiation and growth is also explored. It is concluded that PEO and ethylene oxide-based polymers are less than ideal with respect to this interfacial behavior.« less

Beyond the hydrophobic effect: Critical function of water at biological phase boundaries--A hypothesis.

PubMed

Damodaran, Srinivasan

2015-07-01

Many life-sustaining processes in living cells occur at the membrane-water interface. The pertinent questions that need to be asked are what is the evolutionary reason for biology to choose the membrane-water interface as the site for performing and/or controlling crucial biological reactions and what is the key physical principle that is singular to the membrane-water interface that biology exploits for regulating metabolic processes in cells? In this review, a hypothesis is developed, which espouses that cells control activities of membrane-bound enzymes and receptor activated processes via manipulating the thermodynamic activity of water at the membrane-water interfacial region. In support of this hypothesis, first we establish that the surface pressure of a lipid monolayer is a direct measure of a reduction in the thermodynamic activity of interfacial water. Second, we show that the surface pressure-dependent activation/inactivation of interfacial enzymes is fundamentally related to their dependence on interfacial water activity. We extend this argument to infer that cells might manipulate activities of membrane-associated biological processes via manipulating the activity of interfacial water via localized compression or expansion of the interface. In this paper, we critically analyze literature data on mechano-activation of large pore ion channels in Escherichia coli spheroplasts and G-proteins in reconstituted lipid vesicles, and show that these pressure-induced activation processes are fundamentally and quantitatively related to changes in the thermodynamic state of interfacial water, caused by mechanical stretching of the bilayer. Copyright © 2015 Elsevier B.V. All rights reserved.

A primer on selecting grain boundary sets for comparison of interfacial fracture properties in molecular dynamics simulations

DOE PAGES

Dingreville, Remi; Aksoy, Doruk; Spearot, Douglas E.

2017-08-21

In this study, all grain boundaries are not equal in their predisposition for fracture due to the complex coupling between lattice geometry, interfacial structure, and mechanical properties. The ability to understand these relationships is crucial to engineer materials resilient to grain boundary fracture. Here, a methodology is presented to isolate the role of grain boundary structure on interfacial fracture properties, such as the tensile strength and work of separation, using atomistic simulations. Instead of constructing sets of grain boundary models within the misorientation/structure space by simply varying the misorientation angle around a fixed misorientation axis, the proposed method creates setsmore » of grain boundary models by means of isocurves associated with important fracture-related properties of the adjoining lattices. Such properties may include anisotropic elastic moduli, the Schmid factor for primary slip, and the propensity for simultaneous slip on multiple slip systems. This approach eliminates the effect of lattice properties from the comparative analysis of interfacial fracture properties and thus enables the identification of structure-property relationships for grain boundaries. As an example, this methodology is implemented to study crack propagation along Ni grain boundaries. Segregated H is used as a means to emphasize differences in the selected grain boundary structures while keeping lattice properties fixed.« less

A primer on selecting grain boundary sets for comparison of interfacial fracture properties in molecular dynamics simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dingreville, Remi; Aksoy, Doruk; Spearot, Douglas E.

In this study, all grain boundaries are not equal in their predisposition for fracture due to the complex coupling between lattice geometry, interfacial structure, and mechanical properties. The ability to understand these relationships is crucial to engineer materials resilient to grain boundary fracture. Here, a methodology is presented to isolate the role of grain boundary structure on interfacial fracture properties, such as the tensile strength and work of separation, using atomistic simulations. Instead of constructing sets of grain boundary models within the misorientation/structure space by simply varying the misorientation angle around a fixed misorientation axis, the proposed method creates setsmore » of grain boundary models by means of isocurves associated with important fracture-related properties of the adjoining lattices. Such properties may include anisotropic elastic moduli, the Schmid factor for primary slip, and the propensity for simultaneous slip on multiple slip systems. This approach eliminates the effect of lattice properties from the comparative analysis of interfacial fracture properties and thus enables the identification of structure-property relationships for grain boundaries. As an example, this methodology is implemented to study crack propagation along Ni grain boundaries. Segregated H is used as a means to emphasize differences in the selected grain boundary structures while keeping lattice properties fixed.« less

Tunable anomalous hall effect induced by interfacial catalyst in perpendicular multilayers

NASA Astrophysics Data System (ADS)

Zhang, J. Y.; Peng, W. L.; Sun, Q. Y.; Liu, Y. W.; Dong, B. W.; Zheng, X. Q.; Yu, G. H.; Wang, C.; Zhao, Y. C.; Wang, S. G.

2018-04-01

The interfacial structures, playing a critical role on the transport properties and the perpendicular magnetic anisotropy in thin films and multilayers, can be modified by inserting an ultrathin functional layer at the various interfaces. The anomalous Hall effect (AHE) in the multilayers with core structure of Ta/CoFeB/X/MgO/Ta (X: Hf or Pt) is tuned by interfacial catalytic engineering. The saturation anomalous Hall resistance (RAH) is increased by 16.5% with 0.1 nm Hf insertion compared with the reference sample without insertion. However, the RAH value is decreased by 9.0% with 0.1 nm Pt insertion. The interfacial states were characterized by the X-ray photoelectron spectroscopy (XPS). The XPS results indicate that a strong bonding between Hf and O for Hf insertion, but no bonding between Pt and O for Pt insertion. The bonding between metal and oxygen leads to various oxygen migration behavior at the interfaces. Therefore, the opposite behavior about the RAH originates from the different oxygen behavior due to various interfacial insertion. This work provides a new approach to manipulate spin transport property for the potential applications.

Interfacial behavior of alkaline protease at the air-water and oil-water interfaces

NASA Astrophysics Data System (ADS)

Zhang, Jian; Li, Yanyan; Wang, Jing; Zhang, Yue

2018-03-01

The interfacial behavior of alkaline protease at the air-water and n-hexane-water interfaces was investigated using interfacial tension, dilatational rheology and dynamic light scattering. Additionally, different adsorption models which are Langmuir, Frumkin, Reorientation-A and Reorientation-R were used to fitting the data of equilibrium interfacial tension for further understanding the interfacial behavior of alkaline protease. Data fitting of the equilibrium interfacial tension was achieved by IsoFit software. The results show that the molecules arrangement of the alkaline protease at the n-hexane-water interface is more tightly than at the air-water interface. The data were further analyzed to indicate that the hydrophobic chains of alkaline protease penetrate into oil phase deeper than the air phase. Also data indicate that the electrostatic interactions and hydrophobic interactions at the n-hexane-water interface are stronger than at the air-water interface within molecules of the alkaline protease. Based on comprehensive analysis of the adsorption kinetics and interfacial rheological properties, interfacial structures mechanism of alkaline protease at n-hexane-water and air-water interfaces was proposed.

X-ray crystallographic and MD simulation studies on the mechanism of interfacial activation of a family I.3 lipase with two lids.

PubMed

Angkawidjaja, Clement; Matsumura, Hiroyoshi; Koga, Yuichi; Takano, Kazufumi; Kanaya, Shigenori

2010-07-02

The interfacial activation mechanism of family I.3 lipase from Pseudomonas sp. MIS38 (PML), which has two alpha-helical lids (lid1 and lid2), was investigated using a combination of X-ray crystallography and molecular dynamics (MD) simulation. The crystal structure of PML in an open conformation was determined at 2.1 A resolution in the presence of Ca(2+) and Triton X-100. Comparison of this structure with that in the closed conformation indicates that both lids greatly change their positions and lid1 is anchored by the calcium ion (Ca1) in the open conformation. This structure was not seriously changed even when the protein was dialyzed extensively against the Ca(2+)-free buffer containing Triton X-100 before crystallization, indicating that the open conformation is fairly stable unless a micellar substance is removed. The crystal structure of the PML derivative, in which the active site serine residue (Ser207) is diethylphosphorylated by soaking the crystal of PML in the open conformation in a solution containing diethyl p-nitrophenyl phosphate, was also determined. This structure greatly resembles that in the open conformation, indicating that PML structure in the open conformation represents that in the active form. MD simulation of PML in the open conformation in the absence of micelles showed that lid2 closes first, while lid1 maintains its open conformation. Likewise, MD simulation of PML in the closed conformation in the absence of Ca(2+) and in the presence of octane or trilaurin micelles showed that lid1 opens, while lid2 remains closed. These results suggest that Ca1 functions as a hook for stabilization of a fully opened conformation of lid1 and for initiation of subsequent opening of lid2. Copyright 2010 Elsevier Ltd. All rights reserved.

Effective charges and zeta potentials of oil in water microemulsions in the presence of Hofmeister salts.

PubMed

Dos Santos, Alexandre P; Levin, Yan

2018-06-14

We present a theory which allows us to calculate the effective charge and zeta potential of oil droplets in microemulsions containing Hofmeister salts. A modified Poisson-Boltzmann equation is used to account for the surface and ion polarizations and hydrophobic and dispersion interactions. The ions are classified as kosmotropes and chaotropes according to their Jones-Dole viscosity B coefficient. Kosmotropes stay hydrated and do not enter into the oil phase, while chaotropes can adsorb to the oil-water interface. The effective interaction potentials between ions and oil-water interface are parametrized so as to accurately account for the excess interfacial tension.

Effective charges and zeta potentials of oil in water microemulsions in the presence of Hofmeister salts

NASA Astrophysics Data System (ADS)

dos Santos, Alexandre P.; Levin, Yan

2018-06-01

We present a theory which allows us to calculate the effective charge and zeta potential of oil droplets in microemulsions containing Hofmeister salts. A modified Poisson-Boltzmann equation is used to account for the surface and ion polarizations and hydrophobic and dispersion interactions. The ions are classified as kosmotropes and chaotropes according to their Jones-Dole viscosity B coefficient. Kosmotropes stay hydrated and do not enter into the oil phase, while chaotropes can adsorb to the oil-water interface. The effective interaction potentials between ions and oil-water interface are parametrized so as to accurately account for the excess interfacial tension.

Metal-organic frameworks for lithium ion batteries and supercapacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ke, Fu-Sheng; Wu, Yu-Shan; Deng, Hexiang, E-mail: hdeng@whu.edu.cn

2015-03-15

Porous materials have been widely used in batteries and supercapacitors attribute to their large internal surface area (usually 100–1000 m{sup 2} g{sup −1}) and porosity that can favor the electrochemical reaction, interfacial charge transport, and provide short diffusion paths for ions. As a new type of porous crystalline materials, metal-organic frameworks (MOFs) have received huge attention in the past decade due to their unique properties, i.e. huge surface area (up to 7000 m{sup 2} g{sup −1}), high porosity, low density, controllable structure and tunable pore size. A wide range of applications including gas separation, storage, catalysis, and drug delivery benefitmore » from the recent fast development of MOFs. However, their potential in electrochemical energy storage has not been fully revealed. Herein, the present mini review appraises recent and significant development of MOFs and MOF-derived materials for rechargeable lithium ion batteries and supercapacitors, to give a glimpse into these potential applications of MOFs. - Graphical abstract: MOFs with large surface area and high porosity can offer more reaction sites and charge carriers diffusion path. Thus MOFs are used as cathode, anode, electrolyte, matrix and precursor materials for lithium ion battery, and also as electrode and precursor materials for supercapacitors. - Highlights: • MOFs have potential in electrochemical area due to their high porosity and diversity. • We summarized and compared works on MOFs for lithium ion battery and supercapacitor. • We pointed out critical challenges and provided possible solutions for future study.« less

Engineering the surface of LiCoO 2 electrodes using atomic layer deposition for stable high-voltage lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Jin; Zhao, Jie; Liu, Yayuan

Here, developing advanced technologies to stabilize positive electrodes of lithium ion batteries under high-voltage operation is becoming increasingly important, owing to the potential to achieve substantially enhanced energy density for applications such as portable electronics and electrical vehicles. Here, we deposited chemically inert and ionically conductive LiAlO 2 interfacial layers on LiCoO 2 electrodes using the atomic layer deposition technique. During prolonged cycling at high-voltage, the LiAlO 2 coating not only prevented interfacial reactions between the LiCoO 2 electrode and electrolyte, as confirmed by electrochemical impedance spectroscopy and Raman characterizations, but also allowed lithium ions to freely diffuse into LiCoOmore » 2 without sacrificing the power density. As a result, a capacity value close to 200 mA·h·g –1 was achieved for the LiCoO 2 electrodes with commercial level loading densities, cycled at the cut-off potential of 4.6 V vs. Li +/Li for 50 stable cycles; this represents a 40% capacity gain, compared with the values obtained for commercial samples cycled at the cut-off potential of 4.2 V vs. Li +/Li.« less

Engineering the surface of LiCoO 2 electrodes using atomic layer deposition for stable high-voltage lithium ion batteries

DOE PAGES

Xie, Jin; Zhao, Jie; Liu, Yayuan; ...

2017-07-25

Here, developing advanced technologies to stabilize positive electrodes of lithium ion batteries under high-voltage operation is becoming increasingly important, owing to the potential to achieve substantially enhanced energy density for applications such as portable electronics and electrical vehicles. Here, we deposited chemically inert and ionically conductive LiAlO 2 interfacial layers on LiCoO 2 electrodes using the atomic layer deposition technique. During prolonged cycling at high-voltage, the LiAlO 2 coating not only prevented interfacial reactions between the LiCoO 2 electrode and electrolyte, as confirmed by electrochemical impedance spectroscopy and Raman characterizations, but also allowed lithium ions to freely diffuse into LiCoOmore » 2 without sacrificing the power density. As a result, a capacity value close to 200 mA·h·g –1 was achieved for the LiCoO 2 electrodes with commercial level loading densities, cycled at the cut-off potential of 4.6 V vs. Li +/Li for 50 stable cycles; this represents a 40% capacity gain, compared with the values obtained for commercial samples cycled at the cut-off potential of 4.2 V vs. Li +/Li.« less

Use of Tween Polymer To Enhance the Compatibility of the Li/Electrolyte Interface for the High-Performance and High-Safety Quasi-Solid-State Lithium-Sulfur Battery.

PubMed

Liu, Jie; Qian, Tao; Wang, Mengfan; Zhou, Jinqiu; Xu, Na; Yan, Chenglin

2018-06-07

Lithium metal batteries have attracted increasing attention recently due to their particular advantages in energy density. However, as for their practical application, the development of solid-state lithium metal batteries is restricted because of the poor Li/electrolyte interface, low Li-ion conductivity, and irregular growth of Li dendrites. To address the above issues, we herein report a high Li-ion conductivity and compatible polymeric interfacial layer by grafting tween-20 on active lithium metal. Sequential oxyethylene groups in tween-grafted Li (TG-Li) improve the ion conductivity and the compatibility of the Li/electrolyte interface, which enables low overpotentials and stable performance over 1000 cycles. Consequently, the poly(ethylene oxide)-based solid-state lithium-sulfur battery with TG-Li exhibits a high reversible capacity of 1051.2 mA h g -1 at 0.2 C (1 C = 1675 mA h g -1 ) and excellent stability for 500 cycles at 2 C. The decreasing concentration of the sulfur atom with increasing Ar + sputtering depth indicates that the polymer interfacial layer works well in suppressing polysulfide reduction to Li 2 S/Li 2 S 2 on the metallic Li surface even after long-term cycling.

Magneto-Ionic Control of Interfacial Magnetic Anisotorpy

NASA Astrophysics Data System (ADS)

Bauer, Uwe; Emori, Satoru; Beach, Geoffrey

2014-03-01

Voltage control of magnetism could bring about revolutionary new spintronic memory and logic devices. Here, we examine domain wall (DW) dynamics in ultrathin Co films and nanowires under the influence of a voltage applied across a gadolinium oxide gate dielectric that simultaneously acts as an oxygen ion conductor. We investigate two electrode configurations, one with a continuous gate dielectric and the other with a patterned gate dielectric which exhibits an open oxide edge right underneath the electrode perimeter. We demonstrate that the open oxide edge acts as a fast diffusion path for oxygen ions and allows voltage-induced switching of magnetic anisotropy at the nanoscale by modulating interfacial chemistry rather than charge density. At room temperature this effect is limited to the vicinity of the open oxide edge, but at a temperature of 100°C it allows complete control over magnetic anisotropy across the whole electrode area, due to higher oxygen ion mobility at elevated temperature. We then harness this novel ``magneto-ionic'' effect to create unprecedentedly strong voltage-induced anisotropy modifications of 3000 fJ/Vm and create electrically programmable DW traps with pinning strengths of 650 Oe, enough to bring to a standstill DWs travelling at speeds of at least 20 m/s. This work is supported by the National Science Foundation through grant ECCS-1128439.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, X.J., E-mail: lixj@alum.imr.ac.cn

During the deposition of diamond films on Ti alloy substrates, titanium carbide is a common precipitated phase, preferentially formed at the interfacial region. However, in this case, the precipitation of an ordered structure of titanium carbide has not been reported. In our work, a long periodic ordered structure of TiC has been observed at the deposited diamond film/Ti alloy interface by high resolution transmission electron microscopy (HRTEM). The long periodic ordered structure is identified as 6H-type. The formation mechanism is revealed by comparative studies on the different structures of TiC precipitated under different diamond deposition conditions in terms of depositionmore » time, atmosphere and temperature. A large number of carbon vacancies in the interfacial precipitated TiC phase are verified through electron energy loss spectroscopy (EELS) quantification analysis. However, an ordered arrangement of these carbon vacancies occurs only when the interfacial stress is large enough to induce the precipitation of 6H-type TiC. The supplementary analysis by X-ray diffraction (XRD) further confirms that additional diffraction peaks presented in the XRD patterns are corresponding to the precipitation of 6H-type TiC. - Highlights: •Different structures of TiC are observed during deposited diamond on Ti alloy. •One is common NaCl structure, the other is periodic structure. •The periodic structure is identified as 6H-type by HRTEM. •Carbon vacancies are verified to always exist in the TiC phase. •The precipitation of 6H-type TiC is mainly affected by interfacial stress.« less

Three-Dimensional, Solid-State Mixed Electron-Ion Conductive Framework for Lithium Metal Anode.

PubMed

Xu, Shaomao; McOwen, Dennis W; Wang, Chengwei; Zhang, Lei; Luo, Wei; Chen, Chaoji; Li, Yiju; Gong, Yunhui; Dai, Jiaqi; Kuang, Yudi; Yang, Chunpeng; Hamann, Tanner R; Wachsman, Eric D; Hu, Liangbing

2018-06-13

Solid-state electrolytes (SSEs) have been widely considered as enabling materials for the practical application of lithium metal anodes. However, many problems inhibit the widespread application of solid state batteries, including the growth of lithium dendrites, high interfacial resistance, and the inability to operate at high current density. In this study, we report a three-dimensional (3D) mixed electron/ion conducting framework (3D-MCF) based on a porous-dense-porous trilayer garnet electrolyte structure created via tape casting to facilitate the use of a 3D solid state lithium metal anode. The 3D-MCF was achieved by a conformal coating of carbon nanotubes (CNTs) on the porous garnet structure, creating a composite mixed electron/ion conductor that acts as a 3D host for the lithium metal. The lithium metal was introduced into the 3D-MCF via slow electrochemical deposition, forming a 3D lithium metal anode. The slow lithiation leads to improved contact between the lithium metal anode and garnet electrolyte, resulting in a low resistance of 25 Ω cm 2 . Additionally, due to the continuous CNT coating and its seamless contact with the garnet we observed highly uniform lithium deposition behavior in the porous garnet structure. With the same local current density, the high surface area of the porous garnet framework leads to a higher overall areal current density for stable lithium deposition. An elevated current density of 1 mA/cm 2 based on the geometric area of the cell was demonstrated for continuous lithium cycling in symmetric lithium cells. For battery operation of the trilayer structure, the lithium can be cycled between the 3D-MCF on one side and the cathode infused into the porous structure on the opposite side. The 3D-MCF created by the porous garnet structure and conformal CNT coating provides a promising direction toward new designs in solid-state lithium metal batteries.

Nanoparticle Decoration of Carbon Nanotubes by Sputtering

DTIC Science & Technology

2013-02-01

subsequent coalescence as the mechanism of growth, but focused on per- formance of the metallized arrays rather than processing- structure relationships...dictates its wet- ting behavior; if the interfacial energy is comparable to the surface energy, the metal will avoid contact with the sub- strate and...form an isolated island to minimize interfacial en- ergy. Significantly lower interfacial energy values will drive the metal to spread on the surface—for

Molecular dynamics studies of interfacial water at the alumina surface.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Argyris, Dr. Dimitrios; Ho, Thomas; Cole, David

2011-01-01

Interfacial water properties at the alumina surface were investigated via all-atom equilibrium molecular dynamics simulations at ambient temperature. Al-terminated and OH-terminated alumina surfaces were considered to assess the structural and dynamic behavior of the first few hydration layers in contact with the substrates. Density profiles suggest water layering up to {approx}10 {angstrom} from the solid substrate. Planar density distribution data indicate that water molecules in the first interfacial layer are organized in well-defined patterns dictated by the atomic terminations of the alumina surface. Interfacial water exhibits preferential orientation and delayed dynamics compared to bulk water. Water exhibits bulk-like behavior atmore » distances greater than {approx}10 {angstrom} from the substrate. The formation of an extended hydrogen bond network within the first few hydration layers illustrates the significance of water?water interactions on the structural properties at the interface.« less

Swift heavy ion irradiation effects in Pt/C and Ni/C multilayers

NASA Astrophysics Data System (ADS)

Gupta, Ajay; Pandita, Suneel; Avasthi, D. K.; Lodha, G. S.; Nandedkar, R. V.

1998-12-01

Irradiation effects of 100 MeV Ag ion irradiation on Ni/C and Pt/C multilayers have been studied using X-ray reflectivity measurements. Modifications are observed in both the multilayers at (dE/dx)e values much below the threshold values for Ni and Pt. This effect is attributed to the discontinuous nature of the metal layers. In both the multilayers interfacial roughness increases with irradiation dose. While Ni/C multilayers exhibit large ion-beam induced intermixing, no observable intermixing is observed in the case of Pt/C multilayer. This difference in the behavior of the two systems suggests a significant role for chemically guided defect motion in the mixing process associated with swift heavy ion irradiation.

Effects of crystal-melt interfacial energy anisotropy on dendritic morphology and growth kinetics

NASA Technical Reports Server (NTRS)

Glicksman, M. E.; Singh, N. B.

1989-01-01

Morphological and kinetic studies of succinonitrile, a BCC crystal with a low (0.5 percent) anisotropy and pivalic acid, and FCC crystal with relatively large (5 percent) anisotropy in solid-liquid interfacial energy, show clearly that anisotropy in the solid-liquid interfacial energy does not affect the tip radius-velocity relationship, but has a profound influence on the tip region and the rate of amplification of branching waves. Anisotropy of the solid-liquid interfacial energy may be one of the key factors by which the microstructural characteristics of cast structures reflect individual material behavior, especially crystal symmetry.

Insight into interfacial effect on effective physical properties of fibrous materials. I. The volume fraction of soft interfaces around anisotropic fibers.

PubMed

Xu, Wenxiang; Wang, Han; Niu, Yanze; Bai, Jingtao

2016-01-07

With advances in interfacial properties characterization technologies, the interfacial volume fraction is a feasible parameter for evaluating effective physical properties of materials. However, there is a need to determine the interfacial volume fraction around anisotropic fibers and a need to assess the influence of such the interfacial property on effective properties of fibrous materials. Either ways, the accurate prediction of interfacial volume fraction is required. Towards this end, we put forward both theoretical and numerical schemes to determine the interfacial volume fraction in fibrous materials, which are considered as a three-phase composite structure consisting of matrix, anisotropic hard spherocylinder fibers, and soft interfacial layers with a constant dimension coated on the surface of each fiber. The interfacial volume fraction actually represents the fraction of space not occupied by all hard fibers and matrix. The theoretical scheme that adopts statistical geometry and stereological theories is essentially an analytic continuation from spherical inclusions. By simulating such three-phase chopped fibrous materials, we numerically derive the interfacial volume fraction. The theoretical and numerical schemes provide a quantitative insight that the interfacial volume fraction depends strongly on the fiber geometries like fiber shape, geometric size factor, and fiber size distribution. As a critical interfacial property, the present contribution can be further drawn into assessing effective physical properties of fibrous materials, which will be demonstrated in another paper (Part II) of this series.

Elastic Green’s Function in Anisotropic Bimaterials Considering Interfacial Elasticity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juan, Pierre -Alexandre; Dingreville, Remi

Here, the two-dimensional elastic Green’s function is calculated for a general anisotropic elastic bimaterial containing a line dislocation and a concentrated force while accounting for the interfacial structure by means of a generalized interfacial elasticity paradigm. The introduction of the interface elasticity model gives rise to boundary conditions that are effectively equivalent to those of a weakly bounded interface. The equations of elastic equilibrium are solved by complex variable techniques and the method of analytical continuation. The solution is decomposed into the sum of the Green’s function corresponding to the perfectly bonded interface and a perturbation term corresponding to themore » complex coupling nature between the interface structure and a line dislocation/concentrated force. Such construct can be implemented into the boundary integral equations and the boundary element method for analysis of nano-layered structures and epitaxial systems where the interface structure plays an important role.« less

Elastic Green’s Function in Anisotropic Bimaterials Considering Interfacial Elasticity

DOE PAGES

Juan, Pierre -Alexandre; Dingreville, Remi

2017-09-13

Here, the two-dimensional elastic Green’s function is calculated for a general anisotropic elastic bimaterial containing a line dislocation and a concentrated force while accounting for the interfacial structure by means of a generalized interfacial elasticity paradigm. The introduction of the interface elasticity model gives rise to boundary conditions that are effectively equivalent to those of a weakly bounded interface. The equations of elastic equilibrium are solved by complex variable techniques and the method of analytical continuation. The solution is decomposed into the sum of the Green’s function corresponding to the perfectly bonded interface and a perturbation term corresponding to themore » complex coupling nature between the interface structure and a line dislocation/concentrated force. Such construct can be implemented into the boundary integral equations and the boundary element method for analysis of nano-layered structures and epitaxial systems where the interface structure plays an important role.« less

X-Ray Photoelectron Spectroscopy Study of the Heating Effects on Pd/6H-SiC Schottky Structure

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Knight, Dak

1998-01-01

X-ray photoelectron spectroscopy is used to study the effects of heat treatment on the Pd/6H-SiC Schottky diode structure. After heating the structure at 425 C for 140 h, a very thin surface layer of PdO mixed with SiO(x) formed on the palladium surface of the Schottky structure. Heat treatment promoted interfacial diffusion and reaction which significantly broadened the interfacial region. In the interfacial region, the palladium concentration decreases with depth, and the interfacial products are Pd(x)Si (x = 1,2,3,4). In the high Pd concentration regions, Pd4Si is the major silicide component while gr and Pd2Si are major components in the low Pd concentration region. At the center of the interface, where the total palladium concentration equals that of silicon, the concentrations of palladium associated with various palladium silicides (Pd(x)Si, x= 1,2,3,4) are approximately equal. The surface passivation layer composed of PdO and SiO, may significantly affect the electronic and catalytic properties of the surface of the Schottky diode which plays a major role in gas detection. The electronic properties of the Schottky structure may be dominated by a (Pd+Pd(x)Si)/SiC interface. In order to stabilize the properties of the Schottky structure the surface and interface diffusion and reactions must be controlled.

Elucidating the Irreversible Mechanism and Voltage Hysteresis in Conversion Reaction for High-Energy Sodium-Metal Sulfide Batteries

DOE PAGES

Wang, Jiajun; Wang, Liguang; Eng, Christopher; ...

2017-03-03

We present that irreversible electrochemical behavior and large voltage hysteresis are commonly observed in battery materials, in particular for materials reacting through conversion reaction, resulting in undesirable round-trip energy loss and low coulombic efficiency. Seeking solutions to these challenges relies on the understanding of the underlying mechanism and physical origins. Here, this study combines in operando 2D transmission X-ray microscopy with X-ray absorption near edge structure, 3D tomography, and galvanostatic intermittent titration techniques to uncover the conversion reaction in sodium–metal sulfide batteries, a promising high-energy battery system. This study shows a high irreversible electrochemistry process predominately occurs at first cycle,more » which can be largely linked to Na ion trapping during the first desodiation process and large interfacial ion mobility resistance. Subsequently, phase transformation evolution and electrochemical reaction show good reversibility at multiple discharge/charge cycles due to materials' microstructural change and equilibrium. The origin of large hysteresis between discharge and charge is investigated and it can be attributed to multiple factors including ion mobility resistance at the two-phase interface, intrinsic slow sodium ion diffusion kinetics, and irreversibility as well as ohmic voltage drop and overpotential. In conclusion, this study expects that such understandings will help pave the way for engineering design and optimization of materials microstructure for future-generation batteries.« less

Tunable Interfacial Thermal Conductance by Molecular Dynamics

NASA Astrophysics Data System (ADS)

Shen, Meng

We study the mechanism of tunable heat transfer through interfaces between solids using a combination of non-equilibrium molecular dynamics simulation (NEMD), vibrational mode analysis and wave packet simulation. We investigate how heat transfer through interfaces is affected by factors including pressure, interfacial modulus, contact area and interfacial layer thickness, with an overreaching goal of developing fundamental knowledge that will allow one to tailor thermal properties of interfacial materials. The role of pressure and interfacial stiffness is unraveled by our studies on an epitaxial interface between two Lennard-Jones (LJ) crystals. The interfacial stiffness is varied by two different methods: (i) indirectly by applying pressure which due to anharmonic nature of bonding, increases interfacial stiffness, and (ii) directly by changing the interfacial bonding strength by varying the depth of the potential well of the LJ potential. When the interfacial bonding strength is low, quantitatively similar behavior to pressure tuning is observed when the interfacial thermal conductance is increased by directly varying the potential-well depth parameter of the LJ potential. By contrast, when the interfacial bonding strength is high, thermal conductance is almost pressure independent, and even slightly decreases with increasing pressure. This decrease can be explained by the change in overlap between the vibrational densities of states of the two crystalline materials. The role of contact area is studied by modeling structures comprised of Van der Waals junctions between single-walled nanotubes (SWCNT). Interfacial thermal conductance between SWCNTs is obtained from NEMD simulation as a function of crossing angle. In this case the junction conductance per unit area is essentially a constant. By contrast, interfacial thermal conductance between multiwalled carbon nanotubes (MWCNTs) is shown to increase with diameter of the nanotubes by recent experimental studies [1]. To elucidate this behavior we studied a simplified model comprised of an interface between two stacks of graphene ribbons to mimic the contact between multiwalled nanotubes. Our results, in agreement with experiment, show that the interfacial thermal conductance indeed increases with the number of graphene layers, corresponding to larger diameter and larger number of walls in MWCNT. The role of interfacial layer thickness is investigated by modeling a system of a few layers of graphene sandwiched between two silicon slabs. We show, by wave packet simulation and by theoretical calculation of a spring-mass model, that the transmission coefficient of individual vibrational modes is strongly dependent on the frequency and the number of graphene layers due to coherent interference effects; by contrast, the interfacial thermal conductance obtained in NEMD simulation, which represents an integral over all phonons, is essentially independent of the number of graphene layers, in agreement with recent experiments. Furthermore, when we heat one atomic layer of graphene directly, the effective interfacial conductance associated with heat dissipation to the silicon substrate is very small. We attribute this to the resistance associated with heat transfer between high and low frequency phonon modes within graphene. Finally, we also replaced graphene layers by a few WSe2 sheets and observed that interfacial thermal resistance of a Si/n-WSe2/Si structure increases linearly with interface thickness at least for 1 < n <= 20, indicating diffusive heat transfer mechanism, in contrast to ballistic behavior of a few graphene layers. The corresponding thermal conductivity (0.048 W m-1 K-1) of a few WSe2 layers is rather small. By comparing phonon dispersion of graphene layers and WSe2 sheets, we attribute the diffusive behavior of a few WSe2 sheets to abundant optical phonons at low and medium frequencies leading to very short mean free path. Our computational studies of effects of pressure and structural properties on interfacial thermal conductance provide fundamental insights for tunable heat transfer in nanostructures. [1] Professor D. Y. Li from University of Vanderbilt, private communication (Nov. 14, 2011).

Ordered mesoporous silica prepared by quiescent interfacial growth method - effects of reaction chemistry

PubMed Central

2013-01-01

Acidic interfacial growth can provide a number of industrially important mesoporous silica morphologies including fibers, spheres, and other rich shapes. Studying the reaction chemistry under quiescent (no mixing) conditions is important for understanding and for the production of the desired shapes. The focus of this work is to understand the effect of a number of previously untested conditions: acid type (HCl, HNO3, and H2SO4), acid content, silica precursor type (TBOS and TEOS), and surfactant type (CTAB, Tween 20, and Tween 80) on the shape and structure of products formed under quiescent two-phase interfacial configuration. Results show that the quiescent growth is typically slow due to the absence of mixing. The whole process of product formation and pore structuring becomes limited by the slow interfacial diffusion of silica source. TBOS-CTAB-HCl was the typical combination to produce fibers with high order in the interfacial region. The use of other acids (HNO3 and H2SO4), a less hydrophobic silica source (TEOS), and/or a neutral surfactant (Tweens) facilitate diffusion and homogenous supply of silica source into the bulk phase and give spheres and gyroids with low mesoporous order. The results suggest two distinct regions for silica growth (interfacial region and bulk region) in which the rate of solvent evaporation and local concentration affect the speed and dimension of growth. A combined mechanism for the interfacial bulk growth of mesoporous silica under quiescent conditions is proposed. PMID:24237719

Moisture effect on interfacial integrity of epoxy-bonded system: a hierarchical approach

NASA Astrophysics Data System (ADS)

Tam, Lik-ho; Lun Chow, Cheuk; Lau, Denvid

2018-01-01

The epoxy-bonded system has been widely used in various applications across different scale lengths. Prior investigations have indicated that the moisture-affected interfacial debonding is the major failure mode of such a system, but the fundamental mechanism remains unknown, such as the basis for the invasion of water molecules in the cross-linked epoxy and the epoxy-bonded interface. This prevents us from predicting the long-term performance of the epoxy-related applications under the effect of the moisture. Here, we use full atomistic models to investigate the response of the epoxy-bonded system towards the adhesion test, and provide a detailed analysis of the interfacial integrity under the moisture effect and the associated debonding mechanism. Molecular dynamics simulations show that water molecules affect the hierarchical structure of the epoxy-bonded system at the nanoscale by disrupting the film-substrate interaction and the molecular interaction within the epoxy, which leads to the detachment of the epoxy thin film, and the final interfacial debonding. The simulation results show good agreement with the experimental results of the epoxy-bonded system. Through identifying the relationship between the epoxy structure and the debonding mechanism at multiple scales, it is shown that the hierarchical structure of the epoxy-bonded system is crucial for the interfacial integrity. In particular, the available space of the epoxy-bonded system, which consists of various sizes ranging from the atomistic scale to the macroscale and is close to the interface facilitates the moisture accumulation, leading to a distinct interfacial debonding when compared to the dry scenario.

Interfacial Ferromagnetism in LaNiO3/CaMnO3 Superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grutter, Alexander J.; Yang, Hao; Kirby, B. J.

2013-08-01

We observe interfacial ferromagnetism in superlattices of the paramagnetic metal LaNiO3 and the antiferromagnetic insulator CaMnO3. LaNiO3 exhibits a thickness dependent metal-insulator transition and we find the emergence of ferromagnetism to be coincident with the conducting state of LaNiO3. That is, only superlattices in which the LaNiO3 layers are metallic exhibit ferromagnetism. Using several magnetic probes, we have determined that the ferromagnetism arises in a single unit cell of CaMnO3 at the interface. Together these results suggest that ferromagnetism can be attributed to a double exchange interaction among Mn ions mediated by the adjacent itinerant metal.

Effects of physical and chemical aspects on membrane fouling and cleaning using interfacial free energy analysis in forward osmosis.

PubMed

Zhang, Wanzhu; Dong, Bingzhi

2018-05-20

Natural organic matter (NOM) in micro-polluted water purification using membranes is a critical issue to handle. Understanding the fouling mechanism in the forward osmosis (FO) process, particularly identifying the predominant factor that controls membrane fouling, could have significant effects on exerting the advantages of FO technique. Cellulose triacetate no-woven (CTA-NW) membrane is applied to experiments with a high removal efficiency (> 99%) for the model foulant. Tannic acid (TA) is used as a surrogate foulant for NOM in the membrane fouling process, thus enabling the analysis of the effects of physical and chemical aspects of water flux, retention, and adsorption. The membrane fouling behavior is affected mainly by the combined effects of the osmotic dragging force and the interaction of the pH in the working solution, foulants, and calcium ions, as demonstrated by the water flux loss and the changes of membrane retention and adsorption. The fouled CTA-NW membrane (in PRO mode) could be flux-recovered by > 85% through physical cleaning methods. The interfacial free energy analysis theory was used to analyze the membrane fouling behavior with calculating the interfacial cohesion and adhesion free energies. The cohesion free energy refers to the deposition of foulants (TA or TA combined with calcium ions) on a fouled membrane. In addition, the adhesion free energy could be used to evaluate the interaction between foulants and a clean membrane.

Interaction of a sodium ion with the water liquid-vapor interface

NASA Technical Reports Server (NTRS)

Wilson, M. A.; Pohorille, A.; Pratt, L. R.; MacElroy, R. D. (Principal Investigator)

1989-01-01

Molecular dynamics results are presented for the density profile of a sodium ion near the water liquid-vapor interface at 320 K. These results are compared with the predictions of a simple dielectric model for the interaction of a monovalent ion with this interface. The interfacial region described by the model profile is too narrow and the profile decreases too abruptly near the solution interface. Thus, the simple model does not provide a satisfactory description of the molecular dynamics results for ion positions within two molecular diameters from the solution interface where appreciable ion concentrations are observed. These results suggest that surfaces associated with dielectric models of ionic processes at aqueous solution interfaces should be located at least two molecular diameters inside the liquid phase. A free energy expense of about 2 kcal/mol is required to move the ion within two molecular layers of the free water liquid-vapor interface.

Enhancing Efficiency of Perovskite Solar Cells via Surface Passivation with Graphene Oxide Interlayer.

PubMed

Li, Hao; Tao, Leiming; Huang, Feihong; Sun, Qiang; Zhao, Xiaojuan; Han, Junbo; Shen, Yan; Wang, Mingkui

2017-11-08

Perovskite solar cells have been demonstrated as promising low-cost and highly efficient next-generation solar cells. Enhancing V OC by minimization the interfacial recombination kinetics can further improve device performance. In this work, we for the first time reported on surface passivation of perovskite layers with chemical modified graphene oxides, which act as efficient interlayer to reduce interfacial recombination and enhance hole extraction as well. Our modeling points out that the passivation effect mainly comes from the interaction between functional group (4-fluorophenyl) and under-coordinated Pb ions. The resulting perovskite solar cells achieved high efficient power conversion efficiency of 18.75% with enhanced high open circuit V OC of 1.11 V. Ultrafast spectroscopy, photovoltage/photocurrent transient decay, and electronic impedance spectroscopy characterizations reveal the effective passivation effect and the energy loss mechanism. This work sheds light on the importance of interfacial engineering on the surface of perovskite layers and provides possible ways to improve device efficiency.

Influence of Polymer-Clay Interfacial Interactions on the Ignition Time of Polymer/Clay Nanocomposites

PubMed Central

Zope, Indraneel S.; Yu, Zhong-Zhen

2017-01-01

Metal ions present on smectite clay (montmorillonite) platelets have preferential reactivity towards peroxy/alkoxy groups during polyamide 6 (PA6) thermal decomposition. This changes the decomposition pathway and negatively affects the ignition response of PA6. To restrict these interfacial interactions, high-temperature-resistant polymers such as polyetherimide (PEI) and polyimide (PI) were used to coat clay layers. PEI was deposited on clay by solution-precipitation, whereas PI was deposited through a solution-imidization-precipitation technique before melt blending with PA6. The absence of polymer-clay interfacial interactions has resulted in a similar time-to-ignition of PA6/PEI-clay (133 s) and PA6/PI-clay (139 s) composites as neat PA6 (140 s). On the contrary, PA6 with conventional ammonium-based surfactant modified clay has showed a huge drop in time-to-ignition (81 s), as expected. The experimental evidences provided herein reveal the role of the catalytic activity of clay during the early stages of polymer decomposition. PMID:28800095

Interfacial Constructing Flexible V2O5@Polypyrrole Core-Shell Nanowire Membrane with Superior Supercapacitive Performance.

PubMed

Wang, Jian-Gan; Liu, Huanyan; Liu, Hongzhen; Hua, Wei; Shao, Minhua

2018-06-06

Flexible membrane consisting of ultralong V 2 O 5 @conducting polypyrrole (V 2 O 5 @PPy) core-shell nanowires is prepared by a facile in situ interfacial synthesis approach. The V 2 O 5 is for the first time demonstrated to show versatile function of reactive template to initiate the uniform and conformal polymerization of PPy nanocoating without the need for extra oxidants. The freestanding PPy-encapsulated V 2 O 5 nanowire membrane is of great benefit in achieving strong electrochemical harvest by increasing electrical conductivity, shortening ion/electron transport distance, and enlarging electrode/electrolyte contact area. When evaluated as binder- and additive-free supercapacitor electrodes, the V 2 O 5 @PPy core-shell hybrid delivers a significantly enhanced specific capacitance of 334 F g -1 along with superior rate capability and improved cycling stability. The present work would provide a simple yet powerful interfacial strategy for elaborate constructing V 2 O 5 /conducting polymers toward various energy-storage technologies.

Root Cause Investigation of Lead-Free Solder Joint Interfacial Failures After Multiple Reflows

NASA Astrophysics Data System (ADS)

Li, Yan; Hatch, Olen; Liu, Pilin; Goyal, Deepak

2017-03-01

Solder joint interconnects in three-dimensional (3D) packages with package stacking configurations typically must undergo multiple reflow cycles during the assembly process. In this work, interfacial open joint failures between the bulk solder and the intermetallic compound (IMC) layer were found in Sn-Ag-Cu (SAC) solder joints connecting a small package to a large package after multiple reflow reliability tests. Systematic progressive 3D x-ray computed tomography experiments were performed on both incoming and assembled parts to reveal the initiation and evolution of the open failures in the same solder joints before and after the reliability tests. Characterization studies, including focused ion beam cross-sections, scanning electron microscopy, and energy-dispersive x-ray spectroscopy, were conducted to determine the correlation between IMC phase transformation and failure initiation in the solder joints. A comprehensive failure mechanism, along with solution paths for the solder joint interfacial failures after multiple reflow cycles, is discussed in detail.

Improved alumina scale adhesion of electron beam physical vapor deposited Dy/Hf-doped β-NiAl coatings

NASA Astrophysics Data System (ADS)

Li, Dongqing; Guo, Hongbo; Peng, Hui; Gong, Shengkai; Xu, Huibin

2013-10-01

The cyclic oxidation behavior of Dy/Hf-doped β-NiAl coatings produced by electron beam physical vapor deposition (EB-PVD) was investigated. For the undoped NiAl coating, numerous voids were formed at the alumina scale/coating interface and large rumpling developed in the scale, leading to premature oxide spallation. The addition of Dy and Hf both improved scale adhesion and the alumina scale grown on the NiAl-Hf coating showed better adhesion than that on the NiAl-Dy coating, although the suppressing effect on interfacial void formation and the scale rumpling resistance were stronger in the NiAl-Dy coating. It is proposed that the segregation of Dy and Hf ions at the scale/coating interfaces not only prevent interfacial sulfur segregation but also may directly enhance interfacial adhesion by participating in bonding across the interfaces, and this strengthening effect is relatively stronger for Hf ionic segregation.

Influence of Polymer-Clay Interfacial Interactions on the Ignition Time of Polymer/Clay Nanocomposites.

PubMed

Zope, Indraneel S; Dasari, Aravind; Yu, Zhong-Zhen

2017-08-11

Metal ions present on smectite clay (montmorillonite) platelets have preferential reactivity towards peroxy/alkoxy groups during polyamide 6 (PA6) thermal decomposition. This changes the decomposition pathway and negatively affects the ignition response of PA6. To restrict these interfacial interactions, high-temperature-resistant polymers such as polyetherimide (PEI) and polyimide (PI) were used to coat clay layers. PEI was deposited on clay by solution-precipitation, whereas PI was deposited through a solution-imidization-precipitation technique before melt blending with PA6. The absence of polymer-clay interfacial interactions has resulted in a similar time-to-ignition of PA6/PEI-clay (133 s) and PA6/PI-clay (139 s) composites as neat PA6 (140 s). On the contrary, PA6 with conventional ammonium-based surfactant modified clay has showed a huge drop in time-to-ignition (81 s), as expected. The experimental evidences provided herein reveal the role of the catalytic activity of clay during the early stages of polymer decomposition.

Interfacial bioconjugation on emulsion droplet for biosensors.

PubMed

Zhang, Qifan; Scigliano, Anita; Biver, Tarita; Pucci, Andrea; Swager, Timothy M

2018-04-13

Interfacial bioconjugation methods are developed for intact liquid emulsion droplets. Complex emulsion droplets having internal hydrocarbon and fluorocarbon immiscible structured phases maintain a dynamic interface for controlled interfacial reactivity. The internal morphological change after binding to biomolecules is readily visualized and detected by light transmission, which provides a platform for the formation of inexpensive and portable bio-sensing assays for enzymes, antibodies, nucleic acids and carbohydrates. Copyright © 2018. Published by Elsevier Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laskin, Julia; Johnson, Grant E.; Prabhakaran, Venkateshkumar

Immobilization of complex molecules and clusters on supports plays an important role in a variety of disciplines including materials science, catalysis and biochemistry. In particular, deposition of clusters on surfaces has attracted considerable attention due to their non-scalable, highly size-dependent properties. The ability to precisely control the composition and morphology of clusters and small nanoparticles on surfaces is crucial for the development of next generation materials with rationally tailored properties. Soft- and reactive landing of ions onto solid or liquid surfaces introduces unprecedented selectivity into surface modification by completely eliminating the effect of solvent and sample contamination on the qualitymore » of the film. The ability to select the mass-to-charge ratio of the precursor ion, its kinetic energy and charge state along with precise control of the size, shape and position of the ion beam on the deposition target makes soft-landing an attractive approach for surface modification. High-purity uniform thin films on surfaces generated using mass-selected ion deposition facilitate understanding of critical interfacial phenomena relevant to catalysis, energy generation and storage, and materials science. Our efforts have been directed toward understanding charge retention by soft-landed metal and metal-oxide cluster ions, which may affect both their structure and reactivity. Specifically, we have examined the effect of the surface on charge retention by both positively and negatively charged cluster ions. We found that the electronic properties of the surface play an important role in charge retention by cluster cations. Meanwhile, the electron binding energy is a key factor determining charge retention by cluster anions. These findings provide the scientific foundation for the rational design of interfaces for advanced catalysts and energy storage devices. Further optimization of electrode-electrolyte interfaces for applications in energy storage and electrocatalysis may be achieved by understanding and controlling the properties of soft-landed cluster ions.« less

A correlation between secondary structure and rheological properties of low-density lipoproteins at air/water interfaces.

PubMed

Khattari, Ziad

2017-09-01

The secondary structure of apolipoprotein B-100 is studied within the bulk phase and at the air/water interface. In these "in viro" experiments, infrared reflection absorption spectroscopy (IRRAS) study was performed at the air/water interface while circular dichroism (CD) was conducted in the bulk phase. In the bulk phase, the conformational structure containing a significant amount of β-structure, whereas varying amount of α-helix, unordered structures, and β-sheet were observed at the air/water interface depending on the low-density lipoprotein (LDL) film interfacial pressure. The present IRRAS results demonstrate the importance of interfacial pressure-induced structural conformations on the apoB-100. A correlation between the secondary structure of the apoB-100 protein and the monomolecular film elasticity at the air/water interface was also established. The orientation of apoB-100 with respect to the LDL film-normal was found to depend on the interfacial pressure exhibited by the monomolecular film. These results may shed light on LDL's pivotal role in the progression of atherosclerotic coronary artery disease as demonstrated previously by clinical trials.

Defect engineering in 1D Ti-W oxide nanotube arrays and their correlated photoelectrochemical performance.

PubMed

Abdelhafiz, Ali A; Ganzoury, Mohamed A; Amer, Ahmad W; Faiad, Azza A; Khalifa, Ahmed M; AlQaradawi, Siham Y; El-Sayed, Mostafa A; Alamgir, Faisal M; Allam, Nageh K

2018-04-18

Understanding the nature of interfacial defects of materials is a critical undertaking for the design of high-performance hybrid electrodes for photocatalysis applications. Theoretical and computational endeavors to achieve this have touched boundaries far ahead of their experimental counterparts. However, to achieve any industrial benefit out of such studies, experimental validation needs to be systematically undertaken. In this sense, we present herein experimental insights into the synergistic relationship between the lattice position and oxidation state of tungsten ions inside a TiO2 lattice, and the respective nature of the created defect states. Consequently, a roadmap to tune the defect states in anodically-fabricated, ultrathin-walled W-doped TiO2 nanotubes is proposed. Annealing the nanotubes in different gas streams enabled the engineering of defects in such structures, as confirmed by XRD and XPS measurements. While annealing under hydrogen stream resulted in the formation of abundant Wn+ (n < 6) ions at the interstitial sites of the TiO2 lattice, oxygen- and air-annealing induced W6+ ions at substitutional sites. EIS and Mott-Schottky analyses indicated the formation of deep-natured trap states in the hydrogen-annealed samples, and predominantly shallow donating defect states in the oxygen- and air-annealed samples. Consequently, the photocatalytic performance of the latter was significantly higher than those of the hydrogen-annealed counterparts. Upon increasing the W content, photoelectrochemical performance deteriorated due to the formation of WO3 crystallites that hindered charge transfer through the photoanode, as evident from the structural and chemical characterization. To this end, this study validates the previous theoretical predictions on the detrimental effect of interstitial W ions. In addition, it sheds light on the importance of defect states and their nature for tuning the photoelectrochemical performance of the investigated materials.

Iron-antimony-based hybrid oxides as high-performance anodes for lithium-ion storage

NASA Astrophysics Data System (ADS)

Nguyen, Tuan Loi; Kim, Doo Soo; Hur, Jaehyun; Park, Min Sang; Yoon, Sukeun; Kim, Il Tae

2018-06-01

We report a facile approach to synthesize Fe-Sb-based hybrid oxides nanocomposites consisting of Sb, Sb2O3, and Fe3O4 for use as new anode materials for lithium-ion batteries. The composites are synthesized via galvanic replacement between Fe3+ and Sb at high temperature in triethylene glycol medium. The phase, morphology, and composition changes of the composites involved in the various stages of the replacement reaction are characterized using X-ray diffractometry, high-resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy. The as-prepared composites have different compositions with very small particle sizes (<< 10 nm). The FexSbyOz-18 h composite, for instance, exhibits high capacity, better cyclic stability, and rate performance than other composites, with a highly stable specific capacity of 434 mAh g-1 at 500 cycles. The excellent electrochemical performance can be ascribed to the high interfacial contact area between the nanocomposite and electrolyte, stable structure of the composites owing to a mixture of inactive phases generated by the conversion reaction between Li+ and oxide metal-whose structure serves as an electron conductor, inhibits agglomeration of Sb particles, and acts as an effective buffer against volume change of Sb during cycling-and high Li+ diffusion ability.

Roles of interfacial reaction on mechanical properties of solder interfaces

NASA Astrophysics Data System (ADS)

Liu, Pilin

This study investigated roles of interfacial reaction in fracture and fatigue of solder interconnects. The interfacial reaction phases in the as-reflowed and after aging were examined by cross-sectional transmission electron microscopy (TEM) while interfacial mechanical properties were determined from a flexural peel fracture mechanics technique. Because of their widespread uses in microelectronic packaging, SnPb solder interfaces, and Bi-containing Pb-free solder interfaces were chosen as the subjects of this study. In the interfacial reaction study, we observed a complicated micro structural evolution during solid-state aging of electroless-Ni(P)/SnPb solder interconnects. In as-reflowed condition, the interfacial reaction produced Ni3Sn 4 and P-rich layers. Following overaging, the interfacial microstructure degenerated into a complex multilayer structure consisting of multiple layers of Ni-Sn compounds and transformed Ni-P phases. In SnPb solder interfacial system, fatigue study showed that the overaging of the high P electroless Ni-P/SnPb interconnects resulted in a sharp reduction in the fatigue resistance of the interface in the high crack growth rate regime. Fracture mechanism analysis indicated that the sharp drop in fatigue resistance was triggered by the brittle fracture of the Ni3Sn2 intermetallic phase developed at the overaged interface. The fatigue behavior was strongly dependent on P concentration in electroless Ni. Kirkendall voids were found in the interfacial region after aging, but they did not cause premature fracture of the solder interfaces. In Bi-containing solder interfacial system, we found that Bi segregated to the Cu-intermetallic interface during aging in SnBi/Cu interconnect. This caused serious embrittlement of Sn-Bi/Cu interface. Further aging induced numerous voids along the Cu3Sn/Cu interface. These interfacial voids were different from Kirkendall voids. Their formation was explained on basis of vacancy condensation at the interface as the Bi segregants reduced the number of effective Cu vacancy sink sites and enhanced void nucleation at the interface. The Bi segregation was avoided by replacing the Cu metallization with Ni. It was found that Bi developed a concentration gradient in the Ni 3Sn4 during interfacial reaction, with the Bi concentration falling off to zero as the Ni/IMC interface was approached. Therefore, the inhibition of Bi segregation by Ni was due to the inability of Bi to reach Ni/IMC interface.

Effect of short-chain branching on interfacial polymer structure and dynamics under shear flow.

PubMed

Jeong, Sohdam; Kim, Jun Mo; Cho, Soowon; Baig, Chunggi

2017-11-22

We present a detailed analysis on the effect of short-chain branches on the structure and dynamics of interfacial chains using atomistic nonequilibrium molecular dynamics simulations of confined polyethylene melts in a wide range of shear rates. The intrinsically fast random motions of the short branches constantly disturb the overall chain conformation, leading to a more compact and less deformed chain structure of the short-chain branched (SCB) polymer against the imposed flow field in comparison with the corresponding linear polymer. Moreover, such highly mobile short branches along the backbone of the SCB polymer lead to relatively weaker out-of-plane wagging dynamics of interfacial chains, with highly curvy backbone structures in the intermediate flow regime. In conjunction with the contribution of short branches (as opposed to that of the backbone) to the total interfacial friction between the chains and the wall, the SCB polymer shows a nearly constant behavior in the degree of slip (d s ) with respect to shear rate in the weak-to-intermediate flow regimes. On the contrary, in the strong flow regime where irregular chain rotation and tumbling dynamics occur via intensive dynamical collisions between interfacial chains and the wall, an enhancement effect on the chain detachment from the wall, caused by short branches, leads to a steeper increase in d s for the SCB polymer than for the linear polymer. Remarkably, the SCB chains at the interface exhibit two distinct types of rolling mechanisms along the backbone, with a half-dumbbell mesoscopic structure at strong flow fields, in addition to the typical hairpin-like tumbling behavior displayed by the linear chains.

Interfacial Dirac cones from alternating topological invariant superlattice structures of Bi2Se3.

PubMed

Song, Jung-Hwan; Jin, Hosub; Freeman, Arthur J

2010-08-27

When the three-dimensional topological insulators Bi2Se3 and Bi2Te3 have an interface with vacuum, i.e., a surface, they show remarkable features such as topologically protected and spin-momentum locked surface states. However, for practical applications, one often requires multiple interfaces or channels rather than a single surface. Here, for the first time, we show that an interfacial and ideal Dirac cone is realized by alternating band and topological insulators. The multichannel Dirac fermions from the superlattice structures open a new way for applications such as thermoelectric and spintronics devices. Indeed, utilizing the interfacial Dirac fermions, we also demonstrate the possible power factor improvement for thermoelectric applications.

The crystal structure of the calcium-bound con-G[Q6A] peptide reveals a novel metal-dependent helical trimer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cnudde, Sara E.; Prorok, Mary; Jia, Xaofei

2012-02-15

The ability to form and control both secondary structure and oligomerization in short peptides has proven to be challenging owing to the structural instability of such peptides. The conantokin peptides are a family of {gamma}-carboxyglutamic acid containing peptides produced in the venoms of predatory sea snails of the Conus family. They are examples of short peptides that form stable helical structures, especially in the presence of divalent cations. Both monomeric and dimeric conantokin peptides have been identified and represent a new mechanism of helix association, 'the metallozipper motif' that is devoid of a hydrophobic interface between monomers. In the presentmore » study, a parallel/antiparallel three-helix bundle was identified and its crystal structure determined at high resolution. The three helices are almost perfectly parallel and represent a novel helix-helix association. The trimer interface is dominated by metal chelation between the three helices, and contains no interfacial hydrophobic interactions. It is now possible to produce stable monomeric, dimeric, or trimeric metallozippers depending on the peptide sequence and metal ion. Such structures have important applications in protein design.« less

Probing interfacial reactions with x-ray reflectivity and x-ray reflection interface microscopy : influence of NaCl on the dissolution of orthoclase at pOH2 and 85 {degree} C.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fenter, P.; Lee, S. S.; Park, C.

2010-01-01

The role of electrolyte ions in the dissolution of orthoclase (0 0 1) in 0.01 m NaOH (pOH {approx} 2) at 84 {+-} 1 C is studied using a combination of in-situ X-ray reflectivity (XR) and ex-situ X-ray reflection interface microscopy (XRIM). The real-time XR measurements show characteristic intensity oscillations as a function of time indicative of the successive removal of individual layers. The dissolution rate in 0.01 m NaOH increases approximately linearly with increasing NaCl concentration up to 2 m NaCl. XRIM measurements of the lateral interfacial topography/structure were made for unreacted surfaces and those reacted in 0.01 mmore » NaOH/1.0 m NaCl solution for 15, 30 and 58 min. The XRIM images reveal that the dissolution reaction leads to the formation of micron-scale regions that are characterized by intrinsically lower reflectivity than the unreacted regions, and appears to be nucleated at steps and defect sites. The reflectivity signal from these reacted regions in the presence of NaCl in solution is significantly lower than that calculated from an idealized layer-by-layer dissolution process, as observed previously in 0.1 m NaOH in the absence of added electrolyte. This difference suggests that dissolved NaCl results in a higher terrace reactivity leading to a more three-dimensional process, consistent with the real-time XR measurements. These observations demonstrate the feasibility of XRIM to gain new insights into processes that control interfacial reactivity, specifically the role of electrolytes in feldspar dissolution at alkaline conditions.« less

The Role of Interfaces in Polyethylene/Metal-Oxide Nanocomposites for Ultrahigh-Voltage Insulating Materials.

PubMed

Pourrahimi, Amir Masoud; Olsson, Richard T; Hedenqvist, Mikael S

2018-01-01

Recent progress in the development of polyethylene/metal-oxide nanocomposites for extruded high-voltage direct-current (HVDC) cables with ultrahigh electric insulation properties is presented. This is a promising technology with the potential of raising the upper voltage limit in today's underground/submarine cables, based on pristine polyethylene, to levels where the loss of energy during electric power transmission becomes low enough to ensure intercontinental electric power transmission. The development of HVDC insulating materials together with the impact of the interface between the particles and the polymer on the nanocomposites electric properties are shown. Important parameters from the atomic to the microlevel, such as interfacial chemistry, interfacial area, and degree of particle dispersion/aggregation, are discussed. This work is placed in perspective with important work by others, and suggested mechanisms for improved insulation using nanoparticles, such as increased charge trap density, adsorption of impurities/ions, and induced particle dipole moments are considered. The effects of the nanoparticles and of their interfacial structures on the mechanical properties and the implications of cavitation on the electric properties are also discussed. Although the main interest in improving the properties of insulating polymers has been on the use of nanoparticles, leading to nanodielectrics, it is pointed out here that larger microscopic hierarchical metal-oxide particles with high surface porosity also impart good insulation properties. The impact of the type of particle and its inherent properties (purity and conductivity) on the nanocomposite dielectric and insulating properties are also discussed based on data obtained by a newly developed technique to directly observe the charge distribution on a nanometer scale in the nanocomposite. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An improved interfacial bonding model for material interface modeling

PubMed Central

Lin, Liqiang; Wang, Xiaodu; Zeng, Xiaowei

2016-01-01

An improved interfacial bonding model was proposed from potential function point of view to investigate interfacial interactions in polycrystalline materials. It characterizes both attractive and repulsive interfacial interactions and can be applied to model different material interfaces. The path dependence of work-of-separation study indicates that the transformation of separation work is smooth in normal and tangential direction and the proposed model guarantees the consistency of the cohesive constitutive model. The improved interfacial bonding model was verified through a simple compression test in a standard hexagonal structure. The error between analytical solutions and numerical results from the proposed model is reasonable in linear elastic region. Ultimately, we investigated the mechanical behavior of extrafibrillar matrix in bone and the simulation results agreed well with experimental observations of bone fracture. PMID:28584343

Growth of Au and ZnS nanostructures via engineered peptide and M13 bacteriophage templates.

PubMed

Chung, Sungwook; Chung, Woo-Jae; Wang, Debin; Lee, Seung-Wuk; De Yoreo, James J

2018-04-25

We demonstrate directed nucleation of Au and ZnS patterns on templates comprised of functional peptides and an M13 bacteriophage. We discuss the control over nucleation in terms of the interplay between enhanced ion binding and reduced interfacial energy resulting from the presence of the templates.

Multiscale modeling of electroosmotic flow: Effects of discrete ion, enhanced viscosity, and surface friction

NASA Astrophysics Data System (ADS)

Bhadauria, Ravi; Aluru, N. R.

2017-05-01

We propose an isothermal, one-dimensional, electroosmotic flow model for slit-shaped nanochannels. Nanoscale confinement effects are embedded into the transport model by incorporating the spatially varying solvent and ion concentration profiles that correspond to the electrochemical potential of mean force. The local viscosity is dependent on the solvent local density and is modeled using the local average density method. Excess contributions to the local viscosity are included using the Onsager-Fuoss expression that is dependent on the local ionic strength. A Dirichlet-type boundary condition is provided in the form of the slip velocity that is dependent on the macroscopic interfacial friction. This solvent-surface specific interfacial friction is estimated using a dynamical generalized Langevin equation based framework. The electroosmotic flow of Na+ and Cl- as single counterions and NaCl salt solvated in Extended Simple Point Charge (SPC/E) water confined between graphene and silicon slit-shaped nanochannels are considered as examples. The proposed model yields a good quantitative agreement with the solvent velocity profiles obtained from the non-equilibrium molecular dynamics simulations.

Non-Faradaic Li + Migration and Chemical Coordination across Solid-State Battery Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gittleson, Forrest S.; El Gabaly, Farid

Efficient and reversible charge transfer is essential to realizing high-performance solid-state batteries. Efforts to enhance charge transfer at critical electrode–electrolyte interfaces have proven successful, yet interfacial chemistry and its impact on cell function remains poorly understood. Using X-ray photoelectron spectroscopy combined with electrochemical techniques, we elucidate chemical coordination near the LiCoO 2–LIPON interface, providing experimental validation of space-charge separation. Space-charge layers, defined by local enrichment and depletion of charges, have previously been theorized and modeled, but the unique chemistry of solid-state battery interfaces is now revealed. Here we highlight the non-Faradaic migration of Li+ ions from the electrode to themore » electrolyte, which reduces reversible cathodic capacity by ~15%. Inserting a thin, ion-conducting LiNbO 3 interlayer between the electrode and electrolyte, however, can reduce space-charge separation, mitigate the loss of Li+ from LiCoO 2, and return cathodic capacity to its theoretical value. This work illustrates the importance of interfacial chemistry in understanding and improving solid-state batteries.« less

Crystallization by Particle Attachment in Synthetic, Biogenic, and Geologic Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Yoreo, James J.; Gilbert, Pupa U.; Sommerdijk, Nico

Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. These non-classical pathways to crystallization are diverse, in contrast to classical models that consider the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle attachment processes and show that multiple pathways result from the interplay of free energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects; particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemblemore » behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems and patterns of mineralization in natural environments.« less

A concise review of nanoscopic aspects of bioleaching bacteria-mineral interactions.

PubMed

Diao, Mengxue; Taran, Elena; Mahler, Stephen; Nguyen, Anh V

2014-10-01

Bioleaching is a technology for the recovery of metals from minerals by means of microorganisms, which accelerate the oxidative dissolution of the mineral by regenerating ferric ions. Bioleaching processes take place at the interface of bacteria, sulfide mineral and leaching solution. The fundamental forces between a bioleaching bacterium and mineral surface are central to understanding the intricacies of interfacial phenomena, such as bacterial adhesion or detachment from minerals and the mineral dissolution. This review focuses on the current state of knowledge in the colloidal aspect of bacteria-mineral interactions, particularly for bioleaching bacteria. Special consideration is given to the microscopic structure of bacterial cells and the atomic force microscopy technique used in the quantification of fundamental interaction forces at nanoscale. Copyright © 2014 Elsevier B.V. All rights reserved.

Liquid phase blending of metal-organic frameworks.

PubMed

Longley, Louis; Collins, Sean M; Zhou, Chao; Smales, Glen J; Norman, Sarah E; Brownbill, Nick J; Ashling, Christopher W; Chater, Philip A; Tovey, Robert; Schönlieb, Carola-Bibiane; Headen, Thomas F; Terrill, Nicholas J; Yue, Yuanzheng; Smith, Andrew J; Blanc, Frédéric; Keen, David A; Midgley, Paul A; Bennett, Thomas D

2018-06-15

The liquid and glass states of metal-organic frameworks (MOFs) have recently become of interest due to the potential for liquid-phase separations and ion transport, alongside the fundamental nature of the latter as a new, fourth category of melt-quenched glass. Here we show that the MOF liquid state can be blended with another MOF component, resulting in a domain structured MOF glass with a single, tailorable glass transition. Intra-domain connectivity and short range order is confirmed by nuclear magnetic resonance spectroscopy and pair distribution function measurements. The interfacial binding between MOF domains in the glass state is evidenced by electron tomography, and the relationship between domain size and T g investigated. Nanoindentation experiments are also performed to place this new class of MOF materials into context with organic blends and inorganic alloys.

18O-tracer diffusion along nanoscaled Sc2O3/yttria stabilized zirconia (YSZ) multilayers: on the influence of strain.

PubMed

Aydin, Halit; Korte, Carsten; Janek, Jürgen

2013-06-01

The oxygen tracer diffusion coefficient describing transport along nano-/microscaled YSZ/Sc 2 O 3 multilayers as a function of the thick-ness of the ion-conducting YSZ layers has been measured by isotope exchange depth profiling (IEDP), using secondary ion mass spec-trometry (SIMS). The multilayer samples were prepared by pulsed laser deposition (PLD) on (0001) Al 2 O 3 single crystalline substrates. The values for the oxygen tracer diffusion coefficient were analyzed as a combination of contributions from bulk and interface contributions and compared with results from YSZ/Y 2 O 3 -multilayers with similar microstructure. Using the Nernst-Einstein equation as the relation between diffusivity and electrical conductivity we find very good agreement between conductivity and diffusion data, and we exclude substantial electronic conductivity in the multilayers. The effect of hetero-interface transport can be well explained by a simple interface strain model. As the multilayer samples consist of columnar film crystallites with a defined inter-face structure and texture, we also discuss the influence of this particular microstructure on the interfacial strain.

Plasma transport in an Eulerian AMR code

DOE PAGES

Vold, E. L.; Rauenzahn, R. M.; Aldrich, C. H.; ...

2017-04-04

A plasma transport model has been implemented in an Eulerian AMR radiation-hydrodynamics code, xRage, which includes plasma viscosity in the momentum tensor, viscous dissipation in the energy equations, and binary species mixing with consistent species mass and energy fluxes driven by concentration gradients, ion and electron baro-diffusion terms and temperature gradient forces. The physics basis, computational issues, numeric options, and results from several test problems are discussed. The transport coefficients are found to be relatively insensitive to the kinetic correction factors when the concentrations are expressed with the molar fractions and the ion mass differences are large. The contributions tomore » flow dynamics from plasma viscosity and mass diffusion were found to increase significantly as scale lengths decrease in an inertial confinement fusion relevant Kelvin-Helmholtz instability mix layer. The mixing scale lengths in the test case are on the order of 100 μm and smaller for viscous effects to appear and 10 μm or less for significant ion species diffusion, evident over durations on the order of nanoseconds. The temperature gradient driven mass flux is seen to deplete a high Z tracer ion at the ion shock front. The plasma transport model provides the generation of the atomic mix per unit of interfacial area between two species with no free parameters. The evolution of the total atomic mix then depends also on an accurate resolution or estimate of the interfacial area between the species mixing by plasma transport. High resolution simulations or a more Lagrangian-like treatment of species interfaces may be required to distinguish plasma transport and numerical diffusion in an Eulerian computation of complex and dynamically evolving mix regions.« less

Plasma transport in an Eulerian AMR code

NASA Astrophysics Data System (ADS)

Vold, E. L.; Rauenzahn, R. M.; Aldrich, C. H.; Molvig, K.; Simakov, A. N.; Haines, B. M.

2017-04-01

A plasma transport model has been implemented in an Eulerian AMR radiation-hydrodynamics code, xRage, which includes plasma viscosity in the momentum tensor, viscous dissipation in the energy equations, and binary species mixing with consistent species mass and energy fluxes driven by concentration gradients, ion and electron baro-diffusion terms and temperature gradient forces. The physics basis, computational issues, numeric options, and results from several test problems are discussed. The transport coefficients are found to be relatively insensitive to the kinetic correction factors when the concentrations are expressed with the molar fractions and the ion mass differences are large. The contributions to flow dynamics from plasma viscosity and mass diffusion were found to increase significantly as scale lengths decrease in an inertial confinement fusion relevant Kelvin-Helmholtz instability mix layer. The mixing scale lengths in the test case are on the order of 100 μm and smaller for viscous effects to appear and 10 μm or less for significant ion species diffusion, evident over durations on the order of nanoseconds. The temperature gradient driven mass flux is seen to deplete a high Z tracer ion at the ion shock front. The plasma transport model provides the generation of the atomic mix per unit of interfacial area between two species with no free parameters. The evolution of the total atomic mix then depends also on an accurate resolution or estimate of the interfacial area between the species mixing by plasma transport. High resolution simulations or a more Lagrangian-like treatment of species interfaces may be required to distinguish plasma transport and numerical diffusion in an Eulerian computation of complex and dynamically evolving mix regions.

General theories and features of interfacial thermal transport

NASA Astrophysics Data System (ADS)

Zhou, Hangbo; Zhang, Gang

2018-03-01

A clear understanding and proper control of interfacial thermal transport is important in nanoscale device. In this review, we first discuss the theoretical methods to handle the interfacial thermal transport problem, such as the macroscopic model, molecular dynamics, lattice dynamics and modern quantum transport theories. Then we discuss various effects that can significantly affect the interfacial thermal transport, such as the formation of chemical bonds at interface, defects and interface roughness, strain and substrates, atomic species and mass ratios, structural orientations. Then importantly, we analyze the role of inelastic scatterings at the interface, and discuss its application in thermal rectifications. Finally, the challenges and promising directions are discussed.

Effect of processing on functional properties of animal blood plasma.

PubMed

Del Hoyo, P; Rendueles, M; Díaz, M

2008-04-01

A number of functional and physical properties such as solubility, foam capacity, emulsifying stability and interfacial tension were compared for standard plasma, plasma decationed by ion exchange and plasma deionized by ultrafiltration (UF). The changes in functional properties can determine the use of a protein as an additive to a food product or invalidate its use. All samples had good functional properties and hence could be used in the formulation of food products. Results showed that ion exchange and UF improved emulsifying capacity while having little effect on the other functional properties.

Influence of alkyl chain length and anion species on ionic liquid structure at the graphite interface as a function of applied potential

NASA Astrophysics Data System (ADS)

Li, Hua; Wood, Ross J.; Endres, Frank; Atkin, Rob

2014-07-01

Atomic force microscopy (AFM) force measurements elucidate the effect of cation alkyl chain length and the anion species on ionic liquid (IL) interfacial structure at highly ordered pyrolytic graphite (HOPG) surfaces as a function of potential. Three ILs are examined: 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM] FAP), 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([EMIM] FAP), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM] TFSA). The step-wise force-distance profiles indicate the ILs adopt a multilayered morphology near the surface. When the surface is biased positively or negatively versus Pt quasireference electrode, both the number of steps, and the force required to rupture each step increase, indicating stronger interfacial structure. At all potentials, push-through forces for [HMIM] FAP are the highest, because the long alkyl chain results in strong cohesive interactions between cations, leading to well-formed layers that resist the AFM tip. The most layers are observed for [EMIM] FAP, because the C2 chains are relatively rigid and the dimensions of the cation and anion are similar, facilitating neat packing. [EMIM] TFSA has the smallest push-through forces and fewest layers, and thus the weakest interfacial structure. Surface-tip attractive forces are measured for all ILs. At the same potential, the attractions are the strongest for [EMIM] TFSA and the weakest for [HMIM] FAP because the interfacial layers are better formed for the longer alkyl chain cation. This means interfacial forces are stronger, which masks the weak attractive forces.

Relationship between ion migration and interfacial degradation of CH3NH3PbI3 perovskite solar cells under thermal conditions.

PubMed

Kim, Seongtak; Bae, Soohyun; Lee, Sang-Won; Cho, Kyungjin; Lee, Kyung Dong; Kim, Hyunho; Park, Sungeun; Kwon, Guhan; Ahn, Seh-Won; Lee, Heon-Min; Kang, Yoonmook; Lee, Hae-Seok; Kim, Donghwan

2017-04-26

Organic-inorganic hybrid perovskite solar cells (PSCs) have been extensively studied because of their outstanding performance: a power conversion efficiency exceeding 22% has been achieved. The most commonly used PSCs consist of CH 3 NH 3 PbI 3 (MAPbI 3 ) with a hole-selective contact, such as 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spiro-bifluorene (spiro-OMeTAD), for collecting holes. From the perspective of long-term operation of solar cells, the cell performance and constituent layers (MAPbI 3 , spiro-OMeTAD, etc.) may be influenced by external conditions like temperature, light, etc. Herein, we report the effects of temperature on spiro-OMeTAD and the interface between MAPbI 3 and spiro-OMeTAD in a solar cell. It was confirmed that, at high temperatures (85 °C), I - and CH 3 NH 3 + (MA + ) diffused into the spiro-OMeTAD layer in the form of CH 3 NH 3 I (MAI). The diffused I - ions prevented oxidation of spiro-OMeTAD, thereby degrading the electrical properties of spiro-OMeTAD. Since ion diffusion can occur during outdoor operation, the structural design of PSCs must be considered to achieve long-term stability.

Multifunctional scanning ion conductance microscopy

PubMed Central

Page, Ashley; Unwin, Patrick R.

2017-01-01

Scanning ion conductance microscopy (SICM) is a nanopipette-based technique that has traditionally been used to image topography or to deliver species to an interface, particularly in a biological setting. This article highlights the recent blossoming of SICM into a technique with a much greater diversity of applications and capability that can be used either standalone, with advanced control (potential–time) functions, or in tandem with other methods. SICM can be used to elucidate functional information about interfaces, such as surface charge density or electrochemical activity (ion fluxes). Using a multi-barrel probe format, SICM-related techniques can be employed to deposit nanoscale three-dimensional structures and further functionality is realized when SICM is combined with scanning electrochemical microscopy (SECM), with simultaneous measurements from a single probe opening up considerable prospects for multifunctional imaging. SICM studies are greatly enhanced by finite-element method modelling for quantitative treatment of issues such as resolution, surface charge and (tip) geometry effects. SICM is particularly applicable to the study of living systems, notably single cells, although applications extend to materials characterization and to new methods of printing and nanofabrication. A more thorough understanding of the electrochemical principles and properties of SICM provides a foundation for significant applications of SICM in electrochemistry and interfacial science. PMID:28484332

The High Performance of Crystal Water Containing Manganese Birnessite Cathodes for Magnesium Batteries.

PubMed

Nam, Kwan Woo; Kim, Sangryun; Lee, Soyeon; Salama, Michael; Shterenberg, Ivgeni; Gofer, Yossi; Kim, Joo-Seong; Yang, Eunjeong; Park, Chan Sun; Kim, Ju-Sik; Lee, Seok-Soo; Chang, Won-Seok; Doo, Seok-Gwang; Jo, Yong Nam; Jung, Yousung; Aurbach, Doron; Choi, Jang Wook

2015-06-10

Rechargeable magnesium batteries have lately received great attention for large-scale energy storage systems due to their high volumetric capacities, low materials cost, and safe characteristic. However, the bivalency of Mg(2+) ions has made it challenging to find cathode materials operating at high voltages with decent (de)intercalation kinetics. In an effort to overcome this challenge, we adopt an unconventional approach of engaging crystal water in the layered structure of Birnessite MnO2 because the crystal water can effectively screen electrostatic interactions between Mg(2+) ions and the host anions. The crucial role of the crystal water was revealed by directly visualizing its presence and dynamic rearrangement using scanning transmission electron microscopy (STEM). Moreover, the importance of lowering desolvation energy penalty at the cathode-electrolyte interface was elucidated by working with water containing nonaqueous electrolytes. In aqueous electrolytes, the decreased interfacial energy penalty by hydration of Mg(2+) allows Birnessite MnO2 to achieve a large reversible capacity (231.1 mAh g(-1)) at high operating voltage (2.8 V vs Mg/Mg(2+)) with excellent cycle life (62.5% retention after 10000 cycles), unveiling the importance of effective charge shielding in the host and facile Mg(2+) ions transfer through the cathode's interface.

Self-consistent field model for strong electrostatic correlations and inhomogeneous dielectric media.

PubMed

Ma, Manman; Xu, Zhenli

2014-12-28

Electrostatic correlations and variable permittivity of electrolytes are essential for exploring many chemical and physical properties of interfaces in aqueous solutions. We propose a continuum electrostatic model for the treatment of these effects in the framework of the self-consistent field theory. The model incorporates a space- or field-dependent dielectric permittivity and an excluded ion-size effect for the correlation energy. This results in a self-energy modified Poisson-Nernst-Planck or Poisson-Boltzmann equation together with state equations for the self energy and the dielectric function. We show that the ionic size is of significant importance in predicting a finite self energy for an ion in an inhomogeneous medium. Asymptotic approximation is proposed for the solution of a generalized Debye-Hückel equation, which has been shown to capture the ionic correlation and dielectric self energy. Through simulating ionic distribution surrounding a macroion, the modified self-consistent field model is shown to agree with particle-based Monte Carlo simulations. Numerical results for symmetric and asymmetric electrolytes demonstrate that the model is able to predict the charge inversion at high correlation regime in the presence of multivalent interfacial ions which is beyond the mean-field theory and also show strong effect to double layer structure due to the space- or field-dependent dielectric permittivity.

Structural phase transitions and time-resolved dynamics of solid-supported interfacial methanol observed by reflection electron diffraction

NASA Astrophysics Data System (ADS)

Yang, Ding-Shyue; He, Xing; Wu, Chengyi

Due to their large scattering cross sections with matter, electrons are suitable for contactless probing of solid-supported surface assemblies, especially in a reflection geometry. Direct visualization of assembly structures through electron diffraction further enables studies of ultrafast structural dynamics through the pump-probe scheme as well as discoveries of hidden phase changes in equilibrium that have been obscure in spectroscopic measurements. In this presentation, we report our first observation of unique two-stage transformations of interfacial methanol on smooth hydrophobic surfaces. The finding may reconcile the inconsistent previous reports of the crystallization temperature using various indirect methods. Dynamically, energy transfer across a solid-molecule interface following photoexcitation of the substrate is found to be highly dependent on the structure of interfacial methanol. If it is only 2-dimensionally ordered, as the film thickness increases, a prolonged time in the decrease of diffraction intensity is seen, signifying an inefficient vibrational coupling in the surface normal direction. Implications of the dynamics results and an outlook of interfacial studies using time-resolved and averaged electron diffraction will be discussed. We gratefully acknowledge the support from the R. A. Welch Foundation (Grant No. E-1860), the Donors of the American Chemical Society Petroleum Research Fund (ACS-PRF), and the University of Houston.

Improving Multi-Functional Properties in Polymer Based Nano Composites by Interfacial

NASA Astrophysics Data System (ADS)

Tajaddod, Navid

Polymer nanocomposites (PNCs) have become an area of increasing interest for study in the field of polymer science and technology since the rise of nanotechnology research. Despite the significant amount of progress being made towards producing high quality PNC materials, improvement in the mechanical, electrical, thermal and other functional properties still remain a challenge. To date, these properties are only a fraction of the expected theoretical values predicted for these materials. Development of interfacial regions between the filler and matrix within the composite has been found to be an important focus in terms of processing. Proper interfacial control and development may ensure excellent interaction and property transfer between the filler and polymer matrix in addition to improvement of multi-functional properties of PNCs. The property-structure importance for the existence of the interfacial and interphase region within PNCs is discussed in this thesis work. Two specific PNC systems are selected for study as part of this dissertation in order to understand the effect of interfacial region development on influencing multi-functional property trends. Polyethylene (PE)/boron nitride (BN) and polyacrylonitrile (PAN)/carbon nanotube (CNT) composites were selected to investigate their mechanical performance and thermal and electrical conductivity properties, respectively. For these systems it was found that the interfacial region structure is directly related to the enhancement of the subsequent multi-functional properties.

Molecular dynamics study of interfacial thermal transport between silicene and substrates.

PubMed

Zhang, Jingchao; Hong, Yang; Tong, Zhen; Xiao, Zhihuai; Bao, Hua; Yue, Yanan

2015-10-07

In this work, the interfacial thermal transport across silicene and various substrates, i.e., crystalline silicon (c-Si), amorphous silicon (a-Si), crystalline silica (c-SiO2) and amorphous silica (a-SiO2) are explored by classical molecular dynamics (MD) simulations. A transient pulsed heating technique is applied in this work to characterize the interfacial thermal resistance in all hybrid systems. It is reported that the interfacial thermal resistances between silicene and all substrates decrease nearly 40% with temperature from 100 K to 400 K, which is due to the enhanced phonon couplings from the anharmonicity effect. Analysis of phonon power spectra of all systems is performed to interpret simulation results. Contradictory to the traditional thought that amorphous structures tend to have poor thermal transport capabilities due to the disordered atomic configurations, it is calculated that amorphous silicon and silica substrates facilitate the interfacial thermal transport compared with their crystalline structures. Besides, the coupling effect from substrates can improve the interface thermal transport up to 43.5% for coupling strengths χ from 1.0 to 2.0. Our results provide fundamental knowledge and rational guidelines for the design and development of the next-generation silicene-based nanoelectronics and thermal interface materials.

Intermetallic Growth and Interfacial Properties of the Grain Refiners in Al Alloys.

PubMed

Li, Chunmei; Cheng, Nanpu; Chen, Zhiqian; Xie, Zhongjing; Hui, Liangliang

2018-04-20

Al₃TM(TM = Ti, Zr, Hf, Sc) particles acting as effective grain refiners for Al alloys have been receiving extensive attention these days. In order to judge their nucleation behaviors, first-principles calculations are used to investigate their intermetallic and interfacial properties. Based on energy analysis, Al₃Zr and Al₃Sc are more suitable for use as grain refiners than the other two intermetallic compounds. Interfacial properties show that Al/Al₃TM(TM = Ti, Zr, Hf, Sc) interfaces in I-ter interfacial mode exhibit better interface wetting effects due to larger Griffith rupture work and a smaller interface energy. Among these, Al/Al₃Sc achieves the lowest interfacial energy, which shows that Sc atoms should get priority for occupying interfacial sites. Additionally, Sc-doped Al/Al₃(Zr, Sc) interfacial properties show that Sc can effectively improve the Al/Al₃(Zr, Sc) binding strength with the Al matrix. By combining the characteristics of interfaces with the properties of intermetallics, the core-shell structure with Al₃Zr-core or Al₃Zr(Sc1-1)-core encircled with an Sc-rich shell forms.

Influence of the side chain and substrate on polythiophene thin film surface, bulk, and buried interfacial structures.

PubMed

Xiao, Minyu; Jasensky, Joshua; Zhang, Xiaoxian; Li, Yaoxin; Pichan, Cayla; Lu, Xiaolin; Chen, Zhan

2016-08-10

The molecular structures of organic semiconducting thin films mediate the performance of various devices composed of such materials. To fully understand how the structures of organic semiconductors alter on substrates due to different polymer side chains and different interfacial interactions, thin films of two kinds of polythiophene derivatives with different side-chains, poly(3-hexylthiophene) (P3HT) and poly(3-potassium-6-hexanoate thiophene) (P3KHT), were deposited and compared on various surfaces. A combination of analytical tools was applied in this research: contact angle goniometry and X-ray photoelectron spectroscopy (XPS) were used to characterize substrate dielectric surfaces with varied hydrophobicity for polymer film deposition; X-ray diffraction and UV-vis spectroscopy were used to examine the polythiophene film bulk structure; sum frequency generation (SFG) vibrational spectroscopy was utilized to probe the molecular structures of polymer film surfaces in air and buried solid/solid interfaces. Both side-chain hydrophobicity and substrate hydrophobicity were found to mediate the crystallinity of the polythiophene film, as well as the orientation of the thiophene ring within the polymer backbone at the buried polymer/substrate interface and the polymer thin film surface in air. For the same type of polythiophene film deposited on different substrates, a more hydrophobic substrate surface induced thiophene ring alignment with the surface normal at both the buried interface and on the surface in air. For different films (P3HT vs. P3KHT) deposited on the same dielectric substrate, a more hydrophobic polythiophene side chain caused the thiophene ring to align more towards the surface at the buried polymer/substrate interface and on the surface in air. We believe that the polythiophene surface, bulk, and buried interfacial molecular structures all influence the hole mobility within the polythiophene film. Successful characterization of an organic conducting thin film surface, buried interfacial, and bulk structures is a first crucial step in understanding the structure-function relationship of such films in order to optimize device performance. An in-depth understanding on how the side-chain influences the interfacial and surface polymer orientation will guide the future molecular structure design of organic semiconductors.

Physicochemical properties and interfacial adaptation of root canal sealers.

PubMed

Cañadas, Piedad S; Berástegui, Ester; Gaton-Hernández, Patrícia; Silva, Léa A B; Leite, Giselle A; Silva, Roberto S

2014-01-01

This study compared the physicochemical properties and interfacial adaptation to canal walls of Endo-CPM-Sealer, Sealapex and Activ GP with the well-established AH Plus sealer. The following analyses were performed: radiopacity, pH variation and solubility using samples of each material and scanning electron microscopy of root-filled bovine incisors to evaluate the interfacial adaptation. Data were analyzed by the parametric and no-parametric tests (α=0.05). All materials were in accordance with the ANSI/ADA requirements for radiopacity. Endo-CPM-Sealer presented the lowest radiopacity values and AH Plus was the most radiopaque sealer (p=0.0001). Except for ActiV GP, which was acidic, all other sealers had basic chemical nature and released hydroxyl ions. Regarding solubility, all materials met the ANSI/ADA recommendations, with no statistically significant difference between the sealers (p=0.0834). AH Plus presented the best adaptation to canal walls in the middle (p=0.0023) and apical (p=0.0012) thirds, while the sealers Activ GP and Endo-CPM-Sealer had poor adaptation to the canal walls. All sealers, except for ActiV GP, were alkaline and all of them fulfilled the ANSI/ADA requirements for radiopacity and solubility. Regarding the interfacial adaptation, AH Plus was superior to the others considering the adaptation to the bovine root canal walls.

The effects of interfacial potential on antimicrobial propensity of ZnO nanoparticle

PubMed Central

Arakha, Manoranjan; Saleem, Mohammed; Mallick, Bairagi C.; Jha, Suman

2015-01-01

The work investigates the role of interfacial potential in defining antimicrobial propensity of ZnO nanoparticle (ZnONP) against different Gram positive and Gram negative bacteria. ZnONPs with positive and negative surface potential are tested against different bacteria with varying surface potentials, ranging −14.7 to −23.6 mV. Chemically synthesized ZnONPs with positive surface potential show very high antimicrobial propensity with minimum inhibitory concentration of 50 and 100 μg/mL for Gram negative and positive bacterium, respectively. On other hand, ZnONPs of the same size but with negative surface potential show insignificant antimicrobial propensity against the studied bacteria. Unlike the positively charged nanoparticles, neither Zn2+ ion nor negatively charged ZnONP shows any significant inhibition in growth or morphology of the bacterium. Potential neutralization and colony forming unit studies together proved adverse effect of the resultant nano-bacterial interfacial potential on bacterial viability. Thus, ZnONP with positive surface potential upon interaction with negative surface potential of bacterial membrane enhances production of the reactive oxygen species and exerts mechanical stress on the membrane, resulting in the membrane depolarization. Our results show that the antimicrobial propensity of metal oxide nanoparticle mainly depends upon the interfacial potential, the potential resulting upon interaction of nanoparticle surface with bacterial membrane. PMID:25873247

On the Hofmeister effect: fluctuations at the protein-water interface and the surface tension.

PubMed

Bogár, Ferenc; Bartha, Ferenc; Násztor, Zoltán; Fábián, László; Leitgeb, Balázs; Dér, András

2014-07-24

We performed molecular dynamics simulations on the tryptophane-cage miniprotein using a nonpolarizable force field, in order to model the effect of concentrated water solutions of neutral salts on protein conformation, which is a manifestation of Hofmeister effects. From the equilibrium values and the fluctuations of the solvent accessible surface area of the miniprotein, the salt-induced changes of the mean value of protein-water interfacial tension were determined. At 300 K, the chaotropic ClO4(-) and NO3(-) decreased the interfacial tension according to their position in the Hofmeister series (by approximately 5 and 2.7 mN/m, respectively), while the kosmotropic F(-) increased it (by 1 mN/m). These values were compared to those obtained from the Gibbs equation using the excess surface adsorption calculated from the probability distribution of the water molecules and ions around the miniprotein, and the two sets were found to be very close to each other. Our results present a direct evidence for the central role of interfacial tension and fluctuations at the protein-water interface in Hofmeister phenomena, and provide a computational method for the determination of the protein-water interfacial tension, establishing a link between the phenomenological and microscopic description of protein-water interfaces.

Interfacial structure and electrical properties of ultrathin HfO2 dielectric films on Si substrates by surface sol-gel method

NASA Astrophysics Data System (ADS)

Gong, You-Pin; Li, Ai-Dong; Qian, Xu; Zhao, Chao; Wu, Di

2009-01-01

Ultrathin HfO2 films with about ~3 nm thickness were deposited on n-type (1 0 0) silicon substrates using hafnium chloride (HfCl4) source by the surface sol-gel method and post-deposition annealing (PDA). The interfacial structure and electrical properties of ultrathin HfO2 films were investigated. The HfO2 films show amorphous structures and smooth surface morphologies with a very thin interfacial oxide layer of ~0.5 nm and small surface roughness (~0.45 nm). The 500 °C PDA treatment forms stronger Hf-O bonds, leading to passivated traps, and the interfacial layer is mainly Hf silicate (HfxSiyOz). Equivalent oxide thickness of around 0.84 nm of HfO2/Si has been obtained with a leakage current density of 0.7 A cm-2 at Vfb + 1 V after 500 °C PDA. It was found that the current conduction mechanism of HfO2/Si varied from Schottky-Richardson emission to Fowler-Nordheim tunnelling at an applied higher positive voltage due to the activated partial traps remaining in the ultrathin HfO2 films.

Counting ions and other nucleophiles at surfaces by chemical trapping.

PubMed

Cuccovia, Iolanda Midea; da Silva Lima, Filipe; Chaimovich, Hernan

2017-10-01

The interfaces of membranes and other aggregates are determined by the polarity, electrical charge, molecular volume, degrees of motional freedom and packing density of the head groups of the amphiphiles. These properties also determine the type of bound ion (ion selectivity) and its local density, i.e. concentration defined by choosing an appropriate volume element at the aggregate interface. Bulk and local ion concentrations can differ by orders of magnitude. The relationships between ion (or other compound) concentrations in the bulk solvent and in the interface are complex but, in some cases, well established. As the local ion concentration, rather than that in the bulk, controls a variety of properties of membranes, micelles, vesicles and other objects of theoretical and applied interests, measurement of local (interfacial, bound) ion concentrations is of relevance for understanding and characterizing such aggregates. Many experimental methods for estimating ion distributions between the bulk solution and the interface provide indirect estimates because they are based on concentration-dependent properties, rather than concentration measurements. Dediazoniation, i.e. the loss of N 2 , of a substituted diazophenyl derivative provides a tool for determining the number of nucleophiles (including neutral or negatively charged ions) surrounding the diazophenyl derivative prior to the dediazoniation event. This reaction, defined as chemical trapping, and the appropriate reference points obtained in bulk solution allow direct measurements of local concentrations of a variety of nucleophiles at the surface of membranes and other aggregates. Here we review our contributions of our research group to the use, and understanding, of this method and applications of chemical trapping to the description of local concentrations of ions and other nucleophiles in micelles, reverse micelles, vesicles and solvent mixtures. Among other results, we have shown that interfacial water determines micellar shape, zwitterionic vesicle-forming amphiphiles display ion selectivity and urea does not accumulate at micellar interfaces. We have also shown that reaction products can be predicted from the composition of the initial state, even in non-ideal solvent mixtures, supporting the usefulness of chemical trapping as a method to determine local concentrations. In addition, we have analysed the mechanism of dediazoniation, both on theoretical and experimental basis, and concluded that the formation of a free phenyl cation is not a necessary part of the reaction pathway.

The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 5. Interface Effects

DTIC Science & Technology

1994-04-01

Interfacial Mechanical Properties in Fiber Reinforced Ceramic Composites," 1. Am. Ceram. Soc., 70 (1987) 542-48. [25] P.D. Jero, R.J. Kerans and T.A...Mater., 40 [611251-57 (1992). [16] D.B. Marshall and W. Oliver, "Measurement of Interfacial Mechanical Properties in Fiber-Reinforced Ceramic...Charlottesville. VA 22903, U.S.A. (Received 14 July 1993;fl/al version acepted IS AustrW 1993) Abstract-The interfacial structure / property relationships of a

Hierarchically structured materials for lithium batteries

NASA Astrophysics Data System (ADS)

Xiao, Jie; Zheng, Jianming; Li, Xiaolin; Shao, Yuyan; Zhang, Ji-Guang

2013-10-01

The lithium-ion battery (LIB) is one of the most promising power sources to be deployed in electric vehicles, including solely battery powered vehicles, plug-in hybrid electric vehicles, and hybrid electric vehicles. With the increasing demand for devices of high-energy densities (>500 Wh kg-1), new energy storage systems, such as lithium-oxygen (Li-O2) batteries and other emerging systems beyond the conventional LIB, have attracted worldwide interest for both transportation and grid energy storage applications in recent years. It is well known that the electrochemical performance of these energy storage systems depends not only on the composition of the materials, but also on the structure of the electrode materials used in the batteries. Although the desired performance characteristics of batteries often have conflicting requirements with the micro/nano-structure of electrodes, hierarchically designed electrodes can be tailored to satisfy these conflicting requirements. This work will review hierarchically structured materials that have been successfully used in LIB and Li-O2 batteries. Our goal is to elucidate (1) how to realize the full potential of energy materials through the manipulation of morphologies, and (2) how the hierarchical structure benefits the charge transport, promotes the interfacial properties and prolongs the electrode stability and battery lifetime.

Graphene-enhanced intermolecular interaction at interface between copper- and cobalt-phthalocyanines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dou, Wei-Dong; Center of Super-Diamond and Advanced Films; Huang, Shu-Ping

2015-10-07

Interfacial electronic structures of copper-phthalocyanine (CuPc), cobalt-phthalocyanine (CoPc), and graphene were investigated experimentally by using photoelectron spectroscopy. While the CuPc/graphene interface shows flat band structure and negligible interfacial dipole indicating quite weak molecule-substrate interaction, the CuPc/CoPc/graphene interface shows a large interfacial dipole and obvious energy level bending. Controlled experiments ruled out possible influences from the change in film structure of CuPc and pure π–π interaction between CoPc and CuPc. Analysis based on X-ray photoelectron spectroscopy and density functional theory reveals that the decrease in the work function for the CuPc/CoPc/graphene system is induced by the intermolecular interaction between CuPc andmore » CoPc which is enhanced owning to the peculiar electronic properties at the CoPc-graphene interface.« less

Very Tiny Rocks: Site-Specific, Size-Dependent Reaction Kinetics at Nanoparticle-Water Interfaces

NASA Astrophysics Data System (ADS)

Rustad, J. R.

2008-12-01

One of the most fundamental challenges in geochemistry is to be able to understand the rates and mechanisms of elementary reactions that describe chemical processes occurring at mineral-water interfaces. One of the reasons for the primitive conceptual state of reaction kinetics in solid earth geochemistry is that it is very difficult to identify defensible elementary reactions where theoretical predictions can be made and the results can tested experimentally at the same length and time scale of the prediction. For example, the most fundamental predictor of complexation kinetics in aqueous solution is the characteristic water exchange rate, which are well known for the aquo ions and vary by 20 orders of magnitude even for simple trivalent ions. In contrast, for interfacial reactions, it was not even known whether water exchange rates were faster or slower than equivalent metal sites in solution, prohibiting any quantitive understanding of mineral reaction kinetics at the molecular level. Recent advances in synthesis and characterization of materials at nanometer length scales has been able to bridge the gap in scale, and nanometer-sized minerals have given us our first quantitative understanding of elementary reaction rates for fundamental processes involving water and hydroxide exchange reactions. I describe the results of molecular dynamics calculation and experimental measurement of the rates of water, hydroxide, and proton exchange reactions on nanoparticle surfaces. The calculations already show that transition state theory is completely inadequate to understand the rates of even the simplest elementary reactions. Furthermore, the mechanistic implications of rate parameters such as activation volume and activation enthalpy may be different in moving from aquo ions to interfaces. Is a molecular understanding of geochemical processes really needed? One might have asked a biologist at the turn of the century whether studying the structure of proteins would ever be useful for curing disease. True molecular level understanding of interfacial interactions has the potential to revolutionize geology, allowing unprecedented detail and accuracy in such important contexts as climate reconstruction and tectonic history. Geology has an inevitable molecular future.

Chemistry of the metal-polymer interfacial region.

PubMed

Leidheiser, H; Deck, P D

1988-09-02

In many polymer-metal systems, chemical bonds are formed that involve metal-oxygen-carbon complexes. Infrared and Mössbauer spectroscopic studies indicate that carboxylate groups play an important role in some systems. The oxygen sources may be the polymer, the oxygen present in the oxide on the metal surface, or atmospheric oxygen. Diffusion of metal ions from the substrate into the polymer interphase may occur in some systems that are cured at elevated temperatures. It is unclear whether a similar, less extensive diffusion occurs over long time periods in systems maintained at room temperature. The interfacial region is dynamic, and chemical changes occur with aging at room temperature. Positron annihilation spectroscopy may have application to characterizing the voids at the metal-polymer interface.

Photoinduced Electron Transfer of PAMAM Dendrimer-Zinc(II) Porphyrin Associates at Polarized Liquid|Liquid Interfaces.

PubMed

Nagatani, Hirohisa; Sakae, Hiroki; Torikai, Taishi; Sagara, Takamasa; Imura, Hisanori

2015-06-09

The heterogeneous photoinduced electron-transfer reaction of the ion associates between NH2-terminated polyamidoamine (PAMAM) dendrimers and 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato zinc(II) (ZnTPPS(4-)) was studied at the polarized water|1,2-dichloroethane (DCE) interface. The positive photocurrent arising from the photoreduction of ZnTPPS(4-) by a lipophilic quencher, decamethylferrocene, in the interfacial region was significantly enhanced by the ion association with the PAMAM dendrimers. The photocurrent response of the dendrimer-ZnTPPS(4-) associates was dependent on the pH condition and on the generation of dendrimer. A few cationic additives such as polyallylamine and n-octyltrimethyammonium were also examined as alternatives to the PAMAM dendrimer, but the magnitude of the photocurrent enhancement was rather small. The high photoreactivity of the dendrimer-ZnTPPS(4-) associates was interpreted mainly as a result of the high interfacial concentration of photoreactive porphyrin units associated stably with the dendrimer which was preferably adsorbed at the polarized water|DCE interface. The photochemical data observed in the second and fourth generation PAMAM dendrimer systems demonstrated that the higher generation dendrimer which can incorporate a porphyrin molecule more completely in the interior is less efficient for the photocurrent enhancement at the interface. These results indicated that the photoreactivity of ionic reactant at a polarized liquid|liquid interface can readily be modified via ion association with the charged dendrimer.

Effect of Rare Earth Ions on the Properties of Composites Composed of Ethylene Vinyl Acetate Copolymer and Layered Double Hydroxides

PubMed Central

Wang, Lili; Li, Bin; Zhao, Xiaohong; Chen, Chunxia; Cao, Jingjing

2012-01-01

Background The study on the rare earth (RE)-doped layered double hydroxides (LDHs) has received considerable attention due to their potential applications in catalysts. However, the use of RE-doped LDHs as polymer halogen-free flame retardants was seldom investigated. Furthermore, the effect of rare earth elements on the hydrophobicity of LDHs materials and the compatibility of LDHs/polymer composite has seldom been reported. Methodology/Principal Findings The stearate sodium surface modified Ni-containing LDHs and RE-doped Ni-containing LDHs were rapidly synthesized by a coprecipitation method coupled with the microwave hydrothermal treatment. The influences of trace amounts of rare earth ions La, Ce and Nd on the amount of water molecules, the crystallinity, the morphology, the hydrophobicity of modified Ni-containing LDHs and the adsorption of modifier in the surface of LDHs were investigated by TGA, XRD, TEM, contact angle and IR, respectively. Moreover, the effects of the rare earth ions on the interfacial compatibility, the flame retardancy and the mechanical properties of ethylene vinyl acetate copolymer (EVA)/LDHs composites were also explored in detail. Conclusions/Significance S-Ni0.1MgAl-La displayed more uniform dispersion and better interfacial compatibility in EVA matrix compared with other LDHs. Furthermore, the S-Ni0.1MgAl-La/EVA composite showed the best fire retardancy and mechanical properties in all composites. PMID:22693627

Role of HfO 2/SiO 2 thin-film interfaces in near-ultraviolet absorption and pulsed laser damage

DOE PAGES

Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.; ...

2016-07-15

Here, the role of thin-film interfaces in the near-ultraviolet (near-UV) absorption and pulsed laser-induced damage was studied for ion-beam-sputtered and electron-beam-evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and anmore » E-field peak and average intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-UV, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the codeposition of HfO 2 and SiO 2 materials.« less

Structure-induced switching of interpolymer adhesion at a solid-polymer melt interface.

PubMed

Jiang, Naisheng; Sen, Mani; Zeng, Wenduo; Chen, Zhizhao; Cheung, Justin M; Morimitsu, Yuma; Endoh, Maya K; Koga, Tadanori; Fukuto, Masafumi; Yuan, Guangcui; Satija, Sushil K; Carrillo, Jan-Michael Y; Sumpter, Bobby G

2018-02-14

Here we report a link between the interfacial structure and adhesive property of homopolymer chains physically adsorbed (i.e., via physisorption) onto solids. Polyethylene oxide (PEO) was used as a model and two different chain conformations of the adsorbed polymer were created on silicon substrates via the well-established Guiselin's approach: "flattened chains" which lie flat on the solid and are densely packed, and "loosely adsorbed polymer chains" which form bridges jointing up nearby empty sites on the solid surface and cover the flattened chains. We investigated the adhesion properties of the two different adsorbed chains using a custom-built adhesion testing device. Bilayers of a thick PEO overlayer on top of the flattened chains or loosely adsorbed chains were subjected to the adhesion test. The results revealed that the flattened chains do not show any adhesion even with the chemically identical free polymer on top, while the loosely adsorbed chains exhibit adhesion. Neutron reflectivity experiments corroborated that the difference in the interfacial adhesion is not attributed to the interfacial brodening at the free polymer-adsorbed polymer interface. Instead, coarse-grained molecular dynamics simulation results suggest that the tail parts of the loosely adsorbed chains act as "connector molecules", bridging the free chains and substrate surface and improving the interfacial adhesion. These findings not only shed light on the structure-property relationship at the interface, but also provide a novel approach for developing sticking/anti-sticking technologies through precise control of the interfacial polymer nanostructures.

Interface structure in nanoscale multilayers near continuous-to-discontinuous regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pradhan, P. C.; Majhi, A.; Nayak, M., E-mail: mnayak@rrcat.gov.in

2016-07-28

Interfacial atomic diffusion, reaction, and formation of microstructure in nanoscale level are investigated in W/B{sub 4}C multilayer (ML) system as functions of thickness in ultrathin limit. Hard x-ray reflectivity (XRR) and x-ray diffuse scattering in conjunction with x-ray absorption near edge spectroscopy (XANES) in soft x-ray and hard x-ray regimes and depth profiling x-ray photoelectron spectroscopy (XPS) have been used to precisely evaluate detailed interfacial structure by systematically varying the individual layer thickness from continuous-to-discontinuous regime. It is observed that the interfacial morphology undergoes an unexpected significant modification as the layer thickness varies from continuous-to-discontinuous regime. The interfacial atomic diffusionmore » increases, the physical density of W layer decreases and that of B{sub 4}C layer increases, and further more interestingly the in-plane correlation length decreases substantially as the layer thickness varies from continuous-to-discontinuous regime. This is corroborated using combined XRR and x-ray diffused scattering analysis. XANES and XPS results show formation of more and more tungsten compounds at the interfaces as the layer thickness decreases below the percolation threshold due to increase in the contact area between the elements. The formation of compound enhances to minimize certain degree of disorder at the interfaces in the discontinuous region that enables to maintain the periodic structure in ML. The degree of interfacial atomic diffusion, interlayer interaction, and microstructure is correlated as a function of layer thickness during early stage of film growth.« less

Molecular dynamics simulation of water at mineral surfaces: Structure, dynamics, energetics and hydrogen bonding

NASA Astrophysics Data System (ADS)

Kalinichev, A. G.; Wang, J.; Kirkpatrick, R.

2006-05-01

Fundamental molecular-level understanding of the properties of aqueous mineral interfaces is of great importance for many geochemical and environmental systems. Interaction between water and mineral surfaces substantially affects the properties of both phases, including the reactivity and functionality of the substrate surface, and the structure, dynamics, and energetics of the near surface aqueous phase. Experimental studies of interfacial water structure and dynamics using surface-sensitive techniques such as sum-frequency vibrational spectroscopy or X-ray and neutron reflectivity are not always possible for many practically important substrates, and their results often require interpretation concerning the atomistic mechanisms responsible for the observed behavior. Molecular computer simulations can provide new insight into the underlying molecular- level relationships between the inorganic substrate structure and composition and the structure, ordering, and dynamics of interfacial water. We have performed a series of molecular dynamics (MD) computer simulations of aqueous interfaces with several silicates (quartz, muscovite, and talc) and hydroxides (brucite, portlandite, gibbsite, Ca/Al and Mg/Al double hydroxides) to quantify the effects of the substrate mineral structure and composition on the structural, transport, and thermodynamic properties of water on these mineral surfaces. Due to the prevalent effects of the development of well-interconnected H-bonding networks across the mineral- water interfaces, all the hydroxide surfaces (including a fully hydroxylated quartz surface) show very similar H2O density profiles perpendicular to the interface. However, the predominant orientations of the interfacial H2O molecules and their detailed 2-dimensional near-surface structure and dynamics parallel to the interface are quite different reflecting the differences in the substrate structural charge distribution and the density and orientations of the surface OH groups. The H2O density profiles and other structural and dynamic characteristics of water at the two siloxane surfaces are very different from each other and from the hydroxide surfaces, since the muscovite surface is negatively charged and hydrophilic, while the talc surface is electrostatically neutral and hydrophobic. In general, at hydrophilic neutral surfaces both donating and accepting H-bonds from the H2O molecules are contributing to the development of the interfacial H-bond network, whereas at hydrophilic but charged surfaces only accepting or donating H-bonds with H2O molecules are possible. At the hydrophobic talc surface H-bonds among H2O molecules dominate the interfacial H-bond network and the water-surface interactions are very weak. The first water layer at all substrates is well ordered parallel to the surface, reflecting substrate crystal structures and indicating the reduced translational and orientational mobility of interfacial H2O molecules. At longer time scale (~100ps) their dynamics can be decomposed into a slow, virtually frozen, regime due to the substrate- bound H2O and a faster regime of almost free water reflecting the dynamics far from the surface. At shorter times (>10ps) the two dynamical regimes are superimposed. The much higher ordering of interfacial water (compared to bulk liquid) can not be adequately described as simply "ice-like". To some extent, it rather resembles the behavior of supercooled water.

Intrinsic bond strength of metal films on polymer substrates

NASA Technical Reports Server (NTRS)

Wheeler, Donald R.; Osaki, Hiroyuki

1990-01-01

A semiquantitative method for the measurement of the intrinsic bond strength between elastic substrates and elastic films that fail by brittle fracture is described. Measurements on a polyethylene terephthalate (PET)-Ni couple were used to verify the essential features of the analysis. It was found that the interfacial shear strength of Ni on PET doubled after ion etching.

Experimentally quantifying anion polarizability at the air/water interface.

PubMed

Tong, Yujin; Zhang, Igor Ying; Campen, R Kramer

2018-04-03

The adsorption of large, polarizable anions from aqueous solution on the air/water interface controls important atmospheric chemistry and is thought to resemble anion adsorption at hydrophobic interfaces generally. While the favourability of adsorption of such ions is clear, quantifying adsorption thermodynamics has proven challenging because it requires accurate description of the structure of the anion and its solvation shell at the interface. In principle anion polarizability offers a structural window, but to the best of our knowledge there has so far been no experimental technique that allowed its characterization with interfacial specificity. Here, we meet this challenge using interface-specific vibrational spectroscopy of Cl-O vibrations of the [Formula: see text] anion at the air/water interface and report that the interface breaks the symmetry of the anion, the anisotropy of [Formula: see text]'s polarizability tensor is more than two times larger than in bulk water and concentration dependent, and concentration-dependent polarizability changes are consistent with correlated changes in surface tension.

Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactants

DOE PAGES

Huang, Caili; Forth, Joe; Wang, Weiyu; ...

2017-09-25

Bicontinuous jammed emulsions (or bijels) are tortuous, interconnected structures of two immiscible liquids, kinetically trapped by colloidal particles that are irreversibly bound to the oil–water interface. A wealth of applications has been proposed for bijels in catalysis, energy storage and molecular encapsulation, but large domain sizes (on the order of 5 µm or larger) and difficulty in fabrication pose major barriers to their use. In this paper, we show that bijels with sub-micrometre domains can be formed via homogenization, rather than spinodal decomposition. We achieve this by using nanoparticle surfactants: polymers and nanoparticles of complementary functionality (for example, ion-pairing) thatmore » bind to one another at the oil–water interface. This allows the stabilization of the bijel far from the demixing point of the liquids, with interfacial tensions on the order of 20 mN m -1. Finally, furthermore, our strategy is extremely versatile, as solvent, nanoparticle and ligand can all be varied.« less

Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Caili; Forth, Joe; Wang, Weiyu

Bicontinuous jammed emulsions (or bijels) are tortuous, interconnected structures of two immiscible liquids, kinetically trapped by colloidal particles that are irreversibly bound to the oil–water interface. A wealth of applications has been proposed for bijels in catalysis, energy storage and molecular encapsulation, but large domain sizes (on the order of 5 µm or larger) and difficulty in fabrication pose major barriers to their use. In this paper, we show that bijels with sub-micrometre domains can be formed via homogenization, rather than spinodal decomposition. We achieve this by using nanoparticle surfactants: polymers and nanoparticles of complementary functionality (for example, ion-pairing) thatmore » bind to one another at the oil–water interface. This allows the stabilization of the bijel far from the demixing point of the liquids, with interfacial tensions on the order of 20 mN m -1. Finally, furthermore, our strategy is extremely versatile, as solvent, nanoparticle and ligand can all be varied.« less

Bimodal Control of Heat Transport at Graphene–Metal Interfaces Using Disorder in Graphene

PubMed Central

Kim, Jaehyeon; Khan, Muhammad Ejaz; Ko, Jae-Hyeon; Kim, Jong Hun; Lee, Eui-Sup; Suh, Joonki; Wu, Junqiao; Kim, Yong-Hyun; Park, Jeong Young; Lyeo, Ho-Ki

2016-01-01

Thermal energy transport across the interfaces of physically and chemically modified graphene with two metals, Al and Cu, was investigated by measuring thermal conductance using the time-domain thermoreflectance method. Graphene was processed using a He2+ ion-beam with a Gaussian distribution or by exposure to ultraviolet/O3, which generates structural or chemical disorder, respectively. Hereby, we could monitor changes in the thermal conductance in response to varying degrees of disorder. We find that the measured conductance increases as the density of the physical disorder increases, but undergoes an abrupt modulation with increasing degrees of chemical modification, which decreases at first and then increases considerably. Moreover, we find that the conductance varies inverse proportionally to the average distance between the structural defects in the graphene, implying a strong in-plane influence of phonon kinetics on interfacial heat flow. We attribute the bimodal results to an interplay between the distinct effects on graphene’s vibrational modes exerted by graphene modification and by the scattering of modes. PMID:27698372

Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

PubMed

Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

2016-07-06

Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise.

Disintegration of Meatball Electrodes for LiNi x Mn y Co z O 2 Cathode Materials

DOE PAGES

Xu, R.; de Vasconcelos, L. S.; Shi, J.; ...

2017-05-12

Mechanical degradation of Li-ion batteries caused by the repetitive swelling and shrinking of electrodes upon electrochemical cycles is now well recognized. Structural disintegration of the state-of-art cathode materials of a hierarchical structure is relatively less studied. In this paper, we track the microstructural evolution of different marked regimes in LiNi x Mn y Co z O 2 (NMC) electrodes after lithiation cycles. Decohesion of primary particles constitutes the major mechanical degradation in the NMC materials, which results in the loss of connectivity of the conductive network and impedance increase. We find that the structural disintegration is largely dependent on themore » charging rate – slow charging causes more damage, and is relatively insensitive to the cyclic voltage window. We use finite element modeling to study the evolution of Li concentration and stresses in a NMC secondary particle and employ the cohesive zone model to simulate the interfacial fracture between primary particles. Finally, we reveal that microcracks accumulate and propagate during the cyclic lithiation and delithiation at a slow charging rate.« less

Structure and Orientation of Bovine Lactoferrampin in the Mimetic Bacterial Membrane as Revealed by Solid-State NMR and Molecular Dynamics Simulation

PubMed Central

Tsutsumi, Atsushi; Javkhlantugs, Namsrai; Kira, Atsushi; Umeyama, Masako; Kawamura, Izuru; Nishimura, Katsuyuki; Ueda, Kazuyoshi; Naito, Akira

2012-01-01

Bovine lactoferrampin (LFampinB) is a newly discovered antimicrobial peptide found in the N1-domain of bovine lactoferrin (268–284), and consists of 17 amino-acid residues. It is important to determine the orientation and structure of LFampinB in bacterial membranes to reveal the antimicrobial mechanism. We therefore performed 13C and 31P NMR, 13C-31P rotational echo double resonance (REDOR), potassium ion-selective electrode, and quartz-crystal microbalance measurements for LFampinB with mimetic bacterial membrane and molecular-dynamics simulation in acidic membrane. 31P NMR results indicated that LFampinB caused a defect in mimetic bacterial membranes. Ion-selective electrode measurements showed that ion leakage occurred for the mimetic bacterial membrane containing cardiolipin. Quartz-crystal microbalance measurements revealed that LFampinB had greater affinity to acidic phospholipids than that to neutral phospholipids. 13C DD-MAS and static NMR spectra showed that LFampinB formed an α-helix in the N-terminus region and tilted 45° to the bilayer normal. REDOR dephasing patterns between carbonyl carbon nucleus in LFampinB and phosphorus nuclei in lipid phosphate groups were measured by 13C-31P REDOR and the results revealed that LFampinB is located in the interfacial region of the membrane. Molecular-dynamics simulation showed the tilt angle to be 42° and the rotation angle to be 92.5° for Leu3, which are in excellent agreement with the experimental values. PMID:23083717

Studies on Electrical and Magnetic Properties of Mg-Substituted Nickel Ferrites

NASA Astrophysics Data System (ADS)

Chavan, Pradeep; Naik, L. R.; Belavi, P. B.; Chavan, Geeta; Ramesha, C. K.; Kotnala, R. K.

2017-01-01

The semiconducting polycrystalline ferrite materials with the general formula Ni1- x Mg x Fe2O4 were synthesized by using the solid state reaction method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrographs, and atomic force microscopy techniques were utilized to study the structural parameters. XRD confirms the formation of single phase cubic spinel structure of the ferrites. The crystallite sizes of ferrites determined using the Debye-Scherer formula ranges from 0.963 μm to 1.069 μm. The cation distribution of ferrite shows that Mg2+ ions occupy a tetrahedral site ( A-site) and the Ni2+ ion occupy an octahedral site ( B-site) whereas Fe3+ ions occupies an octahedral as well as a tetrahedral site. The study of elastic parameters such as the longitudinal modulus, rigidity modulus, Young's modulus, bulk modulus, and Debye temperature were estimated using the FTIR technique. The decrease of direct current (DC) resistivity with increase in temperature indicates the semiconducting nature of ferrites. The dielectric constant as well as loss tangent decreases with increase in frequency, and at still higher frequencies, they are almost constant. This shows usual dielectric dispersion behavior attributed to the Maxwell-Wagner type of interfacial polarization and is in accordance with Koop's phenomenological theory. The linear increase of alternating current conductivity with increase of frequency shows the small polaron hopping type of conduction mechanism in all the ferrites. The magnetic properties such as saturation magnetization ( M s ), magnetic moment, coercivity, remnant magnetization ( M r ), and the ratio of M r /M s was estimated using the M-H loop.

Composite electrolytes of polyethylene oxides/garnets interfacially wetted by ionic liquid for room-temperature solid-state lithium battery

NASA Astrophysics Data System (ADS)

Huo, Hanyu; Zhao, Ning; Sun, Jiyang; Du, Fuming; Li, Yiqiu; Guo, Xiangxin

2017-12-01

Paramount attention has been paid on solid polymer electrolytes due to their potential in enhancement of energy density as well as improvement of safety. Herein, the composite electrolytes consisting of Li-salt-free polyethylene oxides and 200 nm-sized Li6.4La3Zr1.4Ta0.6O12 particles interfacially wetted by [BMIM]TF2N of 1.8 μL cm-2 have been prepared. Such wetted ionic liquid remains the solid state of membrane electrolytes and decreases the interface impedance between the electrodes and the electrolytes. There is no release of the liquid phase from the PEO matrix when the pressure of 5.0 × 104 Pa being applied for 24 h. The interfacially wetted membrane electrolytes show the conductivity of 2.2 × 10-4 S cm-1 at 20 °C, which is one order of magnitude greater than that of the membranes without the wetted ionic liquids. The conduction mechanism is related to a large number of lithium ions releasing from Li6.4La3Zr1.4Ta0.6O12 particles and the improved conductive paths along the ion-liquid-wetted interfaces between the polymer matrix and ceramic grains. When the membranes being used in the solid-state LiFePO4/Li and LiFe0.15Mn0.85PO4/Li cells at 25 °C, the excellent rate capability and superior cycle stability has been shown. The results provide a new prospect for solid polymer electrolytes used for room-temperature solid-state lithium batteries.

Interfacially polymerized layers for oxygen enrichment: a method to overcome Robeson's upper-bound limit.

PubMed

Tsai, Ching-Wei; Tsai, Chieh; Ruaan, Ruoh-Chyu; Hu, Chien-Chieh; Lee, Kueir-Rarn

2013-06-26

Interfacial polymerization of four aqueous phase monomers, diethylenetriamine (DETA), m-phenylenediamine (mPD), melamine (Mela), and piperazine (PIP), and two organic phase monomers, trimethyl chloride (TMC) and cyanuric chloride (CC), produce a thin-film composite membrane of polymerized polyamide layer capable of O2/N2 separation. To achieve maximum efficiency in gas permeance and O2/N2 permselectivity, the concentrations of monomers, time of interfacial polymerization, number of reactive groups in monomers, and the structure of monomers need to be optimized. By controlling the aqueous/organic monomer ratio between 1.9 and 2.7, we were able to obtain a uniformly interfacial polymerized layer. To achieve a highly cross-linked layer, three reactive groups in both the aqueous and organic phase monomers are required; however, if the monomers were arranged in a planar structure, the likelihood of structural defects also increased. On the contrary, linear polymers are less likely to result in structural defects, and can also produce polymer layers with moderate O2/N2 selectivity. To minimize structural defects while maximizing O2/N2 selectivity, the planar monomer, TMC, containing 3 reactive groups, was reacted with the semirigid monomer, PIP, containing 2 reactive groups to produce a membrane with an adequate gas permeance of 7.72 × 10(-6) cm(3) (STP) s(-1) cm(-2) cm Hg(-1) and a high O2/N2 selectivity of 10.43, allowing us to exceed the upper-bound limit of conventional thin-film composite membranes.

Interfacial wave theory for dendritic structure of a growing needle crystal. I - Local instability mechanism. II - Wave-emission mechanism at the turning point

NASA Technical Reports Server (NTRS)

Xu, Jian-Jun

1989-01-01

The complicated dendritic structure of a growing needle crystal is studied on the basis of global interfacial wave theory. The local dispersion relation for normal modes is derived in a paraboloidal coordinate system using the multiple-variable-expansion method. It is shown that the global solution in a dendrite growth process incorporates the morphological instability factor and the traveling wave factor.

Computational Modeling of Interfacial Behaviors in Nanocomposite Materials

PubMed Central

Lin, Liqiang; Wang, Xiaodu; Zeng, Xiaowei

2017-01-01

Towards understanding the bulk material response in nanocomposites, an interfacial zone model was proposed to define a variety of material interface behaviors (e.g. brittle, ductile, rubber-like, elastic-perfectly plastic behavior etc.). It also has the capability to predict bulk material response though independently control of the interface properties (e.g. stiffness, strength, toughness). The mechanical response of granular nanocomposite (i.e. nacre) was investigated through modeling the “relatively soft” organic interface as an interfacial zone among “hard” mineral tablets and simulation results were compared with experimental measurements of stress-strain curves in tension and compression tests. Through modeling varies material interfaces, we found out that the bulk material response of granular nanocomposite was regulated by the interfacial behaviors. This interfacial zone model provides a possible numerical tool for qualitatively understanding of structure-property relationships through material interface design. PMID:28983123

Interfacial activity of acid functionalized single-walled carbon nanotubes (SWCNTs) at the fluid-fluid interface

NASA Astrophysics Data System (ADS)

Feng, Tao; Russell, Thomas; Hoagland, David

2013-03-01

Interfacial assembly of acid-functionalized single-walled carbon nanotubes at the oil/water interface is achieved by the addition of low molecular weight (MW) amino-terminated polystyrene in the oil phase. The surface activity of carboxylated SWCNTs is strongly influenced by the end-group chemistry and molecular weight of the polystyrene component, the concentrations of this component and the SWCNTs, along with the degree of functionalization of the SWCNTs. The prerequisites for interfacial trapping are amino termini on chains with MW less than 5K and 6 hours or longer incubation of pristine SWCNTs to achieve their carboxylation. Plummets in interfacial tension resembling those for surfactants were observed at critical bulk concentrations of both SWCNTs and PS-NH2. In dried droplets, SWCNTs densely packed with associated PS-NH2 form a bird nest-like interfacial structure, with the SWCNTs preferentially oriented perpendicular to the original interface. Advisor

Inhomogeneity of block copolymers at the interface of an immiscible polymer blend

NASA Astrophysics Data System (ADS)

Ryu, Ji Ho; Kim, YongJoo; Lee, Won Bo

2018-04-01

We present the effects of structure and stiffness of block copolymers on the interfacial properties of an immiscible homopolymer blend. Diblock and two-arm grafted copolymers with variation in stiffness are modeled using coarse-grained molecular dynamics to compare the compatibilization efficiency, i.e., reduction of interfacial tension. Overall, grafted copolymers are located more compactly at the interface and show better compatibilization efficiency than diblock copolymers. In addition, an increase in the stiffness for one of the blocks of the diblock copolymers causes unusual inhomogeneous interfacial coverage due to bundle formation. However, an increase in the stiffness for one of blocks of the grafted copolymers prevents the bundle formation due to the branched chain. As a result, homogeneous interfacial coverage of homopolymer blends is realized with significant reduction of interfacial tension which makes grafted copolymer a better candidate for the compatibilizer of immiscible homopolymer blend.

Shell structure of natural rubber particles: evidence of chemical stratification by electrokinetics and cryo-TEM.

PubMed

Rochette, Christophe N; Crassous, Jérôme J; Drechsler, Markus; Gaboriaud, Fabien; Eloy, Marie; de Gaudemaris, Benoît; Duval, Jérôme F L

2013-11-26

The interfacial structure of natural rubber (NR) colloids is investigated by means of cryogenic transmission electron microscopy (cryo-TEM) and electrokinetics over a broad range of KNO3 electrolyte concentrations (4-300 mM) and pH values (1-8). The asymptotic plateau value reached by NR electrophoretic mobility (μ) in the thin double layer limit supports the presence of a soft (ion- and water-permeable) polyelectrolytic type of layer located at the periphery of the NR particles. This property is confirmed by the analysis of the electron density profile obtained from cryo-TEM that evidences a ∼2-4 nm thick corona surrounding the NR polyisoprene core. The dependence of μ on pH and salt concentration is further marked by a dramatic decrease of the point of zero electrophoretic mobility (PZM) from 3.6 to 0.8 with increasing electrolyte concentration in the range 4-300 mM. Using a recent theory for electrohydrodynamics of soft multilayered particles, this "anomalous" dependence of the PZM on electrolyte concentration is shown to be consistent with a radial organization of anionic and cationic groups across the peripheral NR structure. The NR electrokinetic response in the pH range 1-8 is indeed found to be equivalent to that of particles surrounded by a positively charged ∼3.5 nm thick layer (mean dissociation pK ∼ 4.2) supporting a thin and negatively charged outermost layer (0.6 nm in thickness, pK ∼ 0.7). Altogether, the strong dependence of the PZM on electrolyte concentration suggests that the electrostatic properties of the outer peripheral region of the NR shell are mediated by lipidic residues protruding from a shell containing a significant amount of protein-like charges. This proposed NR shell interfacial structure questions previously reported NR representations according to which the shell consists of either a fully mixed lipid-protein layer, or a layer of phospholipids residing exclusively beneath an outer proteic film.

Interfacial Bonding Energy on the Interface between ZChSnSb/Sn Alloy Layer and Steel Body at Microscale.

PubMed

Wang, Jianmei; Xia, Quanzhi; Ma, Yang; Meng, Fanning; Liang, Yinan; Li, Zhixiong

2017-09-25

To investigate the performance of bonding on the interface between ZChSnSb/Sn and steel body, the interfacial bonding energy on the interface of a ZChSnSb/Sn alloy layer and the steel body with or without Sn as an intermediate layer was calculated under the same loadcase using the molecular dynamics simulation software Materials Studio by ACCELRYS, and the interfacial bonding energy under different Babbitt thicknesses was compared. The results show that the bonding energy of the interface with Sn as an intermediate layer is 10% larger than that of the interface without a Sn layer. The interfacial bonding performances of Babbitt and the steel body with Sn as an intermediate layer are better than those of an interface without a Sn layer. When the thickness of the Babbitt layer of bushing is 17.143 Å, the interfacial bonding energy reaches the maximum, and the interfacial bonding performance is optimum. These findings illustrate the bonding mechanism of the interfacial structure from the molecular level so as to ensure the good bonding properties of the interface, which provides a reference for the improvement of the bush manufacturing process from the microscopic point of view.

Intermetallic Growth and Interfacial Properties of the Grain Refiners in Al Alloys

PubMed Central

Li, Chunmei; Cheng, Nanpu; Chen, Zhiqian; Xie, Zhongjing; Hui, Liangliang

2018-01-01

Al3TM(TM = Ti, Zr, Hf, Sc) particles acting as effective grain refiners for Al alloys have been receiving extensive attention these days. In order to judge their nucleation behaviors, first-principles calculations are used to investigate their intermetallic and interfacial properties. Based on energy analysis, Al3Zr and Al3Sc are more suitable for use as grain refiners than the other two intermetallic compounds. Interfacial properties show that Al/Al3TM(TM = Ti, Zr, Hf, Sc) interfaces in I-ter interfacial mode exhibit better interface wetting effects due to larger Griffith rupture work and a smaller interface energy. Among these, Al/Al3Sc achieves the lowest interfacial energy, which shows that Sc atoms should get priority for occupying interfacial sites. Additionally, Sc-doped Al/Al3(Zr, Sc) interfacial properties show that Sc can effectively improve the Al/Al3(Zr, Sc) binding strength with the Al matrix. By combining the characteristics of interfaces with the properties of intermetallics, the core-shell structure with Al3Zr-core or Al3Zr(Sc1-1)-core encircled with an Sc-rich shell forms. PMID:29677155

Interfacial energetics of two-dimensional colloidal clusters generated with a tunable anharmonic interaction potential

NASA Astrophysics Data System (ADS)

Hilou, Elaa; Du, Di; Kuei, Steve; Biswal, Sibani Lisa

2018-02-01

Interfacial characteristics are critical to various properties of two-dimensional (2D) materials such as band alignment at a heterojunction and nucleation kinetics in a 2D crystal. Despite the desire to harness these enhanced interfacial properties for engineering new materials, unexpected phase transitions and defects, unique to the 2D morphology, have left a number of open questions. In particular, the effects of configurational anisotropy, which are difficult to isolate experimentally, and their influence on interfacial properties are not well understood. In this work, we begin to probe this structure-thermodynamic relationship, using a rotating magnetic field to generate an anharmonic interaction potential in a 2D system of paramagnetic particles. At low magnetic field strengths, weakly interacting colloidal particles form non-close-packed, fluidlike droplets, whereas, at higher field strengths, crystallites with hexagonal ordering are observed. We examine spatial and interfacial properties of these 2D colloidal clusters by measuring the local bond orientation order parameter and interfacial stiffness as a function of the interaction strength. To our knowledge, this is the first study to measure the tunable interfacial stiffness of a 2D colloidal cluster by controlling particle interactions using external fields.

Electrospun Nanofiber-Coated Membrane Separators for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Lee, Hun

Lithium-ion batteries are widely used as a power source for portable electronic devices and hybrid electric vehicles due to their excellent energy and power densities, long cycle life, and enhanced safety. A separator is considered to be the critical component in lithium-ion rechargeable batteries. The separator is placed between the positive and negative electrodes in order to prevent the physical contact of electrodes while allowing the transportation of ions. In most commercial lithium-ion batteries, polyolefin microporous membranes are commonly used as the separator due to their good chemical stability and high mechanical strength. However, some of their intrinsic natures, such as low electrolyte uptake, poor adhesion property to the electrodes, and low ionic conductivity, can still be improved to achieve higher performance of lithium-ion batteries. In order to improve these intrinsic properties, polyolefin microporous membranes can be coated with nanofibers by using electrospinning technique. Electrospinning is a simple and efficient method to prepare nanofibers which can absorb a significant amount of liquid electrolyte to achieve low internal resistance and battery performance. This research presents the preparation and investigation of composite membrane separators prepared by coating nanofibers onto polyolefin microporous membranes via electrospinning technique. Polyvinylidene fluoride polymers and copolymers were used for the preparation of electrospun nanofiber coatings because they have excellent electrochemical stability, good adhesion property, and high temperature resistance. The nanofiber coatings prepared by electrospinning form an interconnected and randomly orientated structure on the surface of the polyolefin microporous membranes. The size of the nanofibers is on a scale that does not interfere with the micropores in the membrane substrates. The resultant nanofiber-coated membranes have the potential to combine advantages of both the polyolefin separator membranes and the nanoscale fibrous polymer coatings. The polyolefin microporous membranes serve as the supporting substrate which provides the required mechanical strength for the assembling process of lithium-ion batteries. The electrospun nanofiber coatings improve the wettability of the composite membrane separators to the liquid electrolyte, which is desirable for the lithium-ion batteries with high kinetics and good cycling performance. The results show that the nanofiber-coated membranes have enhanced adhesion properties to the battery electrode which can help prevent the formation of undesirable gaps between the separators and electrodes during prolonged charge-discharge cycles, especially in large-format batteries. The improvement on adhesive properties of nanofiber-coated membranes was evaluated by peel test. Nanofiber coatings applied to polyolefin membrane substrates improve the adhesion of separator membranes to battery electrodes. Electrolyte uptakes, ionic conductivities and interfacial resistances of the nanofiber-coated membrane separators were studied by soaking the membrane separators with a liquid electrolyte solution of 1 M lithium hexafluorophosphate dissolved in ethylene carbonate/dimethylcarbonate/ethylmethyl carbonate (1:1:1 vol). The nanofiber coatings on the surface of the membrane substrates increase the electrolyte uptake capacity due to the high surface area and capillary effect of nanofibers. The nanofiber-coated membranes soaked in the liquid electrolyte solution exhibit high ionic conductivities and low interfacial resistances to the lithium electrode. The cells containing LiFePO 4 cathode and the nanofiber-coated membranes as the separator show high discharge specific capacities and good cycling stability at room temperature. The nanofiber coatings on the membrane substrates contribute to high ionic conductivity and good electrochemical performance in lithium-ion batteries. Therefore, these nanofiber-coated composite membranes can be directly used as novel battery separators for high performance of lithium-ion batteries. Coating polyolefin microporous membranes with electrospun nanofibers is a promising approach to obtain highperformance separators for advanced lithium-ion batteries.

Highly improved Uv resistance and composite interfacial properties of aramid fiber via iron (III) coordination

NASA Astrophysics Data System (ADS)

Cheng, Zheng; Hong, Dawei; Dai, Yu; Jiang, Chan; Meng, Chenbo; Luo, Longbo; Liu, Xiangyang

2018-03-01

The poor Uv stability and weak interfacial adhesion are considered as the bottleneck problems for further application of aramid fiber. Herein, a new strategy, Fe3+ coordination, was reported for aramid fiber to simultaneous improve its Uv resistance and composite interfacial shear strength. Fe3+ was introduced onto aramid fiber by coordinating with benzimidazole unit of fiber structure. It can reach a doping capacity of as high as 1516ug/g fiber, and the fiber surface is saturatedly covered with Fe3+. The chemical structure of Fe3+-benzimidazole brings about strong metal-enhanced fluorescence emission effect, which, in turn, greatly raises its Uv stability. Owing to the Fe3+ coordination, the tensile strength of Fe-coordinated fiber could preserve as high as 96% after Uv irradiation, compared with 73% of untreated fiber. Meanwhile, the introduction of Fe3+ improves the surface polarity of aramid fiber and consequently leads to the increase of the composite interfacial shear strength by 39%. It is believed that the Fe-coordinated fiber integrates the advantages of easy production, cost-effective and increased Uv stability, as well as high composite interfacial adhesion, and can be used as promising enhancement for the advanced composite material in harsh environment.

Engineering the biosynthesis of novel rhamnolipids in Escherichia coli for enhanced oil recovery.

PubMed

Han, L; Liu, P; Peng, Y; Lin, J; Wang, Q; Ma, Y

2014-07-01

The interfacial tension of rhamnolipids and their applications in enhanced oil recovery are dependent on their chemical structures and compositions. To improve their performances of interfacial tension and enhanced oil recovery, the engineered strategies were applied to produce novel rhamnolipids with different chemical structures and compositions. By introducing different key genes for rhamnolipid biosynthesis, Escherichia coli was firstly constructed to produce rhamnolipids that showed different performances in interfacial tension from those from Pseudomonas aeruginosa due to the different fatty acyl compositions. Then, the mutant RhlBs were created by directed evolution and subsequent site-directed mutagenesis and resulted in the production of the novel rhamnolipids with the different performances in interfacial tension as well as enhanced oil recovery. Lastly, computational modelling elucidates that the single amino acid mutation at the position 168 in RhlB would change the volume of binding pocket for substrate and thus affect the selectivity of rhamnolipid formation in E. coli. The novel rhamnolipids that showed the improved performances of interfacial tension and the potential different applications in enhanced oil recovery were successfully produced by engineered E. coli. This study proved that the combination of metabolic engineering and protein engineering is an important engineered strategy to produce many novel metabolites in micro-organisms. © 2014 The Society for Applied Microbiology.

Influence of charged defects on the interfacial bonding strength of tantalum- and silver-doped nanograined TiO2.

PubMed

Azadmanjiri, Jalal; Wang, James; Berndt, Christopher C; Kapoor, Ajay; Zhu, De Ming; Ang, Andrew S M; Srivastava, Vijay K

2017-05-17

A nano-grained layer including line defects was formed on the surface of a Ti alloy (Ti alloy , Ti-6Al-4V ELI). Then, the micro- and nano-grained Ti alloy with the formation of TiO 2 on its top surface was coated with a bioactive Ta layer with or without incorporating an antibacterial agent of Ag that was manufactured by magnetron sputtering. Subsequently, the influence of the charged defects (the defects that can be electrically charged on the surface) on the interfacial bonding strength and hardness of the surface system was studied via an electronic model. Thereby, material systems of (i) Ta coated micro-grained titanium alloy (Ta/MGTi alloy ), (ii) Ta coated nano-grained titanium alloy (Ta/NGTi alloy ), (iii) TaAg coated micro-grained titanium alloy (TaAg/MGTi alloy ) and (iv) TaAg coated nano-grained titanium alloy (TaAg/NGTi alloy ) were formed. X-ray photoelectron spectroscopy was used to probe the electronic structure of the micro- and nano-grained Ti alloy , and so-formed heterostructures. The thin film/substrate interfaces exhibited different satellite peak intensities. The satellite peak intensity may be related to the interfacial bonding strength and hardness of the surface system. The interfacial layer of TaAg/NGTi alloy exhibited the highest satellite intensity and maximum hardness value. The increased bonding strength and hardness in the TaAg/NGTi alloy arises due to the negative core charge of the dislocations and neighbor space charge accumulation, as well as electron accumulation in the created semiconductor phases of larger band gap at the interfacial layer. These two factors generate interfacial polarization and enhance the satellite intensity. Consequently, the interfacial bonding strength and hardness of the surface system are improved by the formation of mixed covalent-ionic bonding structures around the dislocation core area and the interfacial layer. The bonding strength relationship by in situ XPS on the metal/TiO 2 interfacial layer may be examined with other noble metals and applied in diverse fields.

Ordered patterns and structures via interfacial self-assembly: superlattices, honeycomb structures and coffee rings.

PubMed

Ma, Hongmin; Hao, Jingcheng

2011-11-01

Self-assembly is now being intensively studied in chemistry, physics, biology, and materials engineering and has become an important "bottom-up" approach to create intriguing structures for different applications. Self-assembly is not only a practical approach for creating a variety of nanostructures, but also shows great superiority in building hierarchical structures with orders on different length scales. The early work in self-assembly focused on molecular self-assembly in bulk solution, including the resultant dye aggregates, liposomes, vesicles, liquid crystals, gels and so on. Interfacial self-assembly has been a great concern over the last two decades, largely because of the unique and ingenious roles of this method for constructing materials at interfaces, such as self-assembled monolayers, Langmuir-Blodgett films, and capsules. Nanocrystal superlattices, honeycomb films and coffee rings are intriguing structural materials with more complex features and can be prepared by interfacial self-assembly on different length scales. In this critical review, we outline the recent development in the preparation and application of colloidal nanocrystal superlattices, honeycomb-patterned macroporous structures by the breath figure method, and coffee-ring-like patterns (247 references). This journal is © The Royal Society of Chemistry 2011

Fabricating small-scale, curved, polymeric structures with convex and concave menisci through interfacial free energy equilibrium.

PubMed

Cheng, Chao-Min; Matsuura, Koji; Wang, I-Jan; Kuroda, Yuka; LeDuc, Philip R; Naruse, Keiji

2009-11-21

Polymeric curved structures are widely used in imaging systems including optical fibers and microfluidic channels. Here, we demonstrate that small-scale, poly(dimethylsiloxane) (PDMS)-based, curved structures can be fabricated through controlling interfacial free energy equilibrium. Resultant structures have a smooth, symmetric, curved surface, and may be convex or concave in form based on surface tension balance. Their curvatures are controlled by surface characteristics (i.e., hydrophobicity and hydrophilicity) of the molds and semi-liquid PDMS. In addition, these structures are shown to be biocompatible for cell culture. Our system provides a simple, efficient and economical method for generating integrateable optical components without costly fabrication facilities.

Review of model sensor studies on Pd/SnO2(110) surfaces

NASA Technical Reports Server (NTRS)

Fryberger, Teresa B.; Semancik, Steve

1990-01-01

Studies performed at the National Institute of Standards and Technology on the model gas sensor system, Pd/SnO2(110), are reviewed. Adsorption and interfacial effects play a primary role in the gas sensing process, as they do in catalysis. For this reason, researchers have used a variety of surface sensitive techniques in the research, including x ray and ultraviolet photoelectron spectroscopies (XPS and UPS), low energy electron diffraction (LEED), and ion scattering spectroscopy (ISS). By combining these complementary techniques with in situ gas response (conductance) measurements, researchers were able to correlate directly sensor activity with the composition and structure of the Pd/SnO2 interface. Although the intent of this work is to develop an understanding of gas sensing mechanisms, its relevance to Pt/SnO2 catalytic systems is obvious.

Protein Monolayer Formation at Air-Electrolyte Interface:. a Langmuir-Blodgett Study

NASA Astrophysics Data System (ADS)

Pal, Prabir; Kamilya, Tapanendu; Mahato, Mrityunjoy; Talapatra, G. B.

The interfacial surface activity of a protein, ovalbumin (OVA) at bare air/water interface in presence and also in absence of electrolyte (KCl) in subphase has been investigated. The surface activity was measured as a function of time. It has been found that, the presence of KCl in aqueous subphase enhances the adsorption rate of the protein. The changes of area/molecule, compressibility, rigidity and unfolding of OVA are trivial up to 10 mM KCl concentration. These properties of OVA, above 10 mM KCl concentration are significant and have been explained in the perspective of DLVO theory and many-body ion-protein dispersion potentials. The presence of high concentration of electrolyte increases the β-structure of OVA, resulting into larger unfolding as well as larger intermolecular aggregates. The overall study indicates that KCl perturbs the OVA monolayer.

CRYSTAL GROWTH. Crystallization by particle attachment in synthetic, biogenic, and geologic environments.

PubMed

De Yoreo, James J; Gilbert, Pupa U P A; Sommerdijk, Nico A J M; Penn, R Lee; Whitelam, Stephen; Joester, Derk; Zhang, Hengzhong; Rimer, Jeffrey D; Navrotsky, Alexandra; Banfield, Jillian F; Wallace, Adam F; Michel, F Marc; Meldrum, Fiona C; Cölfen, Helmut; Dove, Patricia M

2015-07-31

Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. The particles involved in these nonclassical pathways to crystallization are diverse, in contrast to classical models that consider only the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle-attachment processes and show that multiple pathways result from the interplay of free-energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects, particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemble behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems, biominerals, and patterns of mineralization in natural environments. Copyright © 2015, American Association for the Advancement of Science.

TEM Analysis of Diffusion-Bonded Silicon Carbide Ceramics Joined Using Metallic Interlayers

NASA Technical Reports Server (NTRS)

Ozaki, T.; Hasegawa, Y.; Tsuda, H.; Mori, S.; Halbig, M. C.; Asthana, R.; Singh, M.

2017-01-01

SiC fiber-bonded ceramics (SA-Tyrannohex: SA-THX) diffusion-bonded with TiCu metallic interlayers were investigated. Thin samples of the ceramics were prepared with a focused ion beam (FIB) and the interfacial microstructure of the prepared samples was studied by transmission electron microscopy (TEM) and scanning TEM (STEM). In addition to conventional microstructure observation, for detailed analysis of reaction compounds in diffusion-bonded area, we performed STEM-EDS measurements and selected area electron diffraction (SAD) experiments. The TEM and STEM experiments revealed the diffusion-bonded area was composed of only one reaction layer, which was characterized by TiC precipitates in Cu-Si compound matrix. This reaction layer was in good contact with the SA-THX substrates, and it is concluded that the joint structure led to the excellent bonding strength.

Bioinspired Nanocellulose Based Hybrid Materials With Novel Interfacial Properties

NASA Astrophysics Data System (ADS)

Keten, Sinan

This talk will overview a simulation-based approach to enhancing the mechanical properties of nanocomposites by utilizing cellulose - the most abundant and renewable structural biopolymer found on our planet. Cellulose nanocrystals (CNCs) exhibit outstanding mechanical properties exceeding that of Kevlar, serving as reinforcing domains in nature's toughest hierarchical nanocomposites such as wood. Yet, weak interfaces at the surfaces of CNCs have so far made it impossible to scale these inherent properties to macroscopic systems. In this work, I will discuss how surface functionalization of CNCs influences their properties in their self-assembled films and nanocomposites with engineered polymer matrices . Specifically, the role of ion exchange based surface modifications and polymer conjugation will be discussed, where atomistic and coarse-grained simulations will reveal new insights into how superior mechanical properties can potentially be attained by hybrid constructs.

Nonlinear optical studies of aqueous interfaces, polymers, and nanowires

NASA Astrophysics Data System (ADS)

Onorato, Robert Michael

Understanding the structure and composition of aqueous interfaces is one of the most important current problems in modern science. Aqueous interfaces are ubiquitous in Nature, ranging from aerosols to cellular structures. Aerosol chemistry is presently the most significant unknown factor in predicting climate change, and an understanding of the chemistry that occurs at aerosol interfaces would significantly improve climate models. Similarly, the nature of aqueous biological interfaces has a profound effect on the structure and function of proteins and other biological structures. Despite the importance of these problems, aqueous interfaces remain incompletely understood due to the challenges of experimentally probing them. Recent experimental and theoretical results have firmly established the existence of enhanced concentrations of selected ions at the air/water interface. In this dissertation, I use an interface-specific technique, UV second harmonic generation (SHG), to further investigate the adsorption of ions to the air/water interface and to extend the study of ion adsorption towards more biologically relevant systems, alcohol/water interfaces. In Chapter 2, I describe resonant UV-SHG studies of the strongly chaotropic thiocyanate ion adsorbed to the interface formed by water and a monolayer of dodecanol, wherein the Gibbs free energy of adsorption was determined to be -6.7 +/- 1.1 and -6.3 +/- 1.8 kJ/mol for sodium and potassium thiocyanate, respectively, coincident with the value determined for thiocyanate at the air/water interface. Interestingly, at concentrations near and above 4 M, the resonant SHG signal increases discontinuously, indicating a structural change in the interfacial region. Recent experimental and theoretical work has demonstrated that the adsorption of bromide is particularly important for chemical reactions on atmospheric aerosols, including the depletion of ozone. In Chapter 3, UV-SHG resonant with the bromide charge-transfer-to-solvent band and a Langmuir adsorption model are used to determine the affinity of bromide for both the air/water and dodecanol/water interfaces in the molar concentration regime. The Gibbs free energy of adsorption for the former is determined to be -1.4 kJ/mol with a lower 90% confidence limit of -4.1 kJ/mol. For the dodecanol/water interface the data are best fit with a Gibbs free energy of +8 kJ/mol with an estimated a lower limit of -4 kJ/mol. Adsorption of ions to the air/water interface in the millimolar regime is a particularly interesting phenomenon. In Chapter 4, the affinity of sodium chloride and sodium bromide to the air/water interface is probed by UV-SHG. Both salts exhibit a strong adsorption, with free energies greater than -20 kJ/mol. Interestingly, sodium chloride exhibits a stronger affinity for the interface than does sodium iodide, which was previously studied by Poul Peterson. This is counter to both experimental and theoretical results for higher concentrations. It has been predicted that ion adsorption is dictated by strong and opposing electrostatic and entropic forces. The change in order of ion interfacial affinity can be explained by relatively small changes in these forces at different concentrations and ionic strengths. In Chapters 5 and 6, other work using nonlinear optical techniques is described. Coherent anti-Stokes Raman scattering microscopy is a promising tool for chemically selective imaging based on molecular vibrations. While CARS is currently used as a biological imaging tool, many variations are still being developed, perhaps the most important being multiplex CARS microscopy. Multiplex CARS has the advantage of comparing images based on different molecular vibrations without changing the excitation wavelengths. In Chapter 5, I demonstrate both high spectral and spatial resolution multiplex CARS imaging of polymer films using a simple scheme for chirped CARS with a spectral bandwidth of 300 cm-1. In Chapter 6, the nonlinear optical properties of KNbO3 nanowires are studied. Using SHG and sum frequency generation, efficient nonlinear optical frequency conversion is demonstrated in single KNbO3 nanowires that act as optical waveguides, yielding a coherent tunable subwavelength light source.

Effects of the c-Si/a-SiO2 interfacial atomic structure on its band alignment: an ab initio study.

PubMed

Zheng, Fan; Pham, Hieu H; Wang, Lin-Wang

2017-12-13

The crystalline-Si/amorphous-SiO 2 (c-Si/a-SiO 2 ) interface is an important system used in many applications, ranging from transistors to solar cells. The transition region of the c-Si/a-SiO 2 interface plays a critical role in determining the band alignment between the two regions. However, the question of how this interface band offset is affected by the transition region thickness and its local atomic arrangement is yet to be fully investigated. Here, by controlling the parameters of the classical Monte Carlo bond switching algorithm, we have generated the atomic structures of the interfaces with various thicknesses, as well as containing Si at different oxidation states. A hybrid functional method, as shown by our calculations to reproduce the GW and experimental results for bulk Si and SiO 2 , was used to calculate the electronic structure of the heterojunction. This allowed us to study the correlation between the interface band characterization and its atomic structures. We found that although the systems with different thicknesses showed quite different atomic structures near the transition region, the calculated band offset tended to be the same, unaffected by the details of the interfacial structure. Our band offset calculation agrees well with the experimental measurements. This robustness of the interfacial electronic structure to its interfacial atomic details could be another reason for the success of the c-Si/a-SiO 2 interface in Si-based electronic applications. Nevertheless, when a reactive force field is used to generate the a-SiO 2 and c-Si/a-SiO 2 interfaces, the band offset significantly deviates from the experimental values by about 1 eV.

Effects of the c-Si/a-SiO 2 interfacial atomic structure on its band alignment: an ab initio study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Fan; Pham, Hieu H.; Wang, Lin-Wang

The crystalline-Si/amorphous-SiO 2 (c-Si/a-SiO 2) interface is an important system used in many applications, ranging from transistors to solar cells. The transition region of the c-Si/a-SiO 2 interface plays a critical role in determining the band alignment between the two regions. However, the question of how this interface band offset is affected by the transition region thickness and its local atomic arrangement is yet to be fully investigated. Here in this study, by controlling the parameters of the classical Monte Carlo bond switching algorithm, we have generated the atomic structures of the interfaces with various thicknesses, as well as containingmore » Si at different oxidation states. A hybrid functional method, as shown by our calculations to reproduce the GW and experimental results for bulk Si and SiO 2, was used to calculate the electronic structure of the heterojunction. This allowed us to study the correlation between the interface band characterization and its atomic structures. We found that although the systems with different thicknesses showed quite different atomic structures near the transition region, the calculated band offset tended to be the same, unaffected by the details of the interfacial structure. Our band offset calculation agrees well with the experimental measurements. This robustness of the interfacial electronic structure to its interfacial atomic details could be another reason for the success of the c-Si/a-SiO 2 interface in Si-based electronic applications. Nevertheless, when a reactive force field is used to generate the a-SiO 2 and c-Si/a-SiO 2 interfaces, the band offset significantly deviates from the experimental values by about 1 eV« less

Effects of the c-Si/a-SiO 2 interfacial atomic structure on its band alignment: an ab initio study

DOE PAGES

Zheng, Fan; Pham, Hieu H.; Wang, Lin-Wang

2017-11-13

The crystalline-Si/amorphous-SiO 2 (c-Si/a-SiO 2) interface is an important system used in many applications, ranging from transistors to solar cells. The transition region of the c-Si/a-SiO 2 interface plays a critical role in determining the band alignment between the two regions. However, the question of how this interface band offset is affected by the transition region thickness and its local atomic arrangement is yet to be fully investigated. Here in this study, by controlling the parameters of the classical Monte Carlo bond switching algorithm, we have generated the atomic structures of the interfaces with various thicknesses, as well as containingmore » Si at different oxidation states. A hybrid functional method, as shown by our calculations to reproduce the GW and experimental results for bulk Si and SiO 2, was used to calculate the electronic structure of the heterojunction. This allowed us to study the correlation between the interface band characterization and its atomic structures. We found that although the systems with different thicknesses showed quite different atomic structures near the transition region, the calculated band offset tended to be the same, unaffected by the details of the interfacial structure. Our band offset calculation agrees well with the experimental measurements. This robustness of the interfacial electronic structure to its interfacial atomic details could be another reason for the success of the c-Si/a-SiO 2 interface in Si-based electronic applications. Nevertheless, when a reactive force field is used to generate the a-SiO 2 and c-Si/a-SiO 2 interfaces, the band offset significantly deviates from the experimental values by about 1 eV« less

First-Order Interfacial Transformations with a Critical Point: Breaking the Symmetry at a Symmetric Tilt Grain Boundary

NASA Astrophysics Data System (ADS)

Yang, Shengfeng; Zhou, Naixie; Zheng, Hui; Ong, Shyue Ping; Luo, Jian

2018-02-01

First-order interfacial phaselike transformations that break the mirror symmetry of the symmetric ∑5 (210 ) tilt grain boundary (GB) are discovered by combining a modified genetic algorithm with hybrid Monte Carlo and molecular dynamics simulations. Density functional theory calculations confirm this prediction. This first-order coupled structural and adsorption transformation, which produces two variants of asymmetric bilayers, vanishes at an interfacial critical point. A GB complexion (phase) diagram is constructed via semigrand canonical ensemble atomistic simulations for the first time.

Effect of the tapered end of a FRP plate on the interfacial stresses in a strengthened beam used in civil engineering applications

NASA Astrophysics Data System (ADS)

Mahi, B. E.; Benrahou, K. H.; Belakhdar, Kh.; Tounsi, A.; Bedia, E. A. Adda

2014-09-01

The interfacial stresses of a beam strengthened with a FRP plate, which is widely employed in the civil engineering for rehabilitation and retrofitting of conventional structures, is investigated. An important feature of the reinforced beam is significant stress concentrations in the adhesive at the ends of the FRP plate. To reduce these interfacial stresses, a FRP plate with a tapered end is often used. The finite-difference method is utilized in this work to predict the distribution of interfacial stresses in beams strengthened with a FRP plate having a tapered end. Numerical results from the analysis are presented to demonstrate the advantages of using tapers in the design of strengthened beams.

Computation of Anisotropic Bi-Material Interfacial Fracture Parameters and Delamination Creteria

NASA Technical Reports Server (NTRS)

Chow, W-T.; Wang, L.; Atluri, S. N.

1998-01-01

This report documents the recent developments in methodologies for the evaluation of the integrity and durability of composite structures, including i) the establishment of a stress-intensity-factor based fracture criterion for bimaterial interfacial cracks in anisotropic materials (see Sec. 2); ii) the development of a virtual crack closure integral method for the evaluation of the mixed-mode stress intensity factors for a bimaterial interfacial crack (see Sec. 3). Analytical and numerical results show that the proposed fracture criterion is a better fracture criterion than the total energy release rate criterion in the characterization of the bimaterial interfacial cracks. The proposed virtual crack closure integral method is an efficient and accurate numerical method for the evaluation of mixed-mode stress intensity factors.

Interfacial behaviour of biopolymer multilayers: Influence of in vitro digestive conditions.

PubMed

Corstens, Meinou N; Osorio Caltenco, Lilia A; de Vries, Renko; Schroën, Karin; Berton-Carabin, Claire C

2017-05-01

Although multilayered emulsions have been related to reduced lipolysis, the involved interfacial phenomena have never been studied directly. In this work, we systematically built multilayers of whey protein and pectin, which we further subjected to digestive conditions, using two different techniques: droplet volume tensiometry to investigate interfacial rheology, and reflectometry to determine the amount of adsorbed material. Interfacial tension and dilatational rheology were linked to adsorption/desorption kinetics measured under static in vitro conditions. The interfacial tension and rheology of the multilayers was rather similar to those found for single whey protein layers, as well as their resistance to duodenal conditions and lipolytic components, which is explained by the rapid destabilisation of multilayers at neutral pH. Sequential adsorption of bile extract or lipase to pre-adsorbed films rapidly lowered the interfacial tension via co-adsorption and displacement, forming a viscoelastic film with low mechanical strength, and highly dynamic adsorption/desorption. When both were present, bile salts dominated the initial adsorption, followed by lipase co-adsorption and formation of lipolysis products that further lowered the interfacial tension, forming a complex interface (including biopolymers, bile salts, lipase, and lipolysis products), independent of pre-adsorbed biopolymer layers. Our study shows that the combination of drop volume tensiometry and reflectometry can be used to study complex interfacial behaviours under digestive conditions, which can lead to smart design of interfacial structures for controlled lipolysis in food emulsions. Copyright © 2017 Elsevier B.V. All rights reserved.

Exploration of the Detailed Conditions for Reductive Stability of Mg(TFSI) 2 in Diglyme: Implications for Multivalent Electrolytes

DOE PAGES

Baskin, Artem; Prendergast, David

2016-02-05

In this paper, we reveal the general mechanisms of partial reduction of multivalent complex cations in conditions specific for the bulk solvent and in the vicinity of the electrified metal electrode surface and disclose the factors affecting the reductive stability of electrolytes for multivalent electrochemistry. Using a combination of ab initio techniques, we clarify the relation between the reductive stability of contact-ion pairs comprising a multivalent cation and a complex anion, their solvation structures, solvent dynamics, and the electrode overpotential. We found that for ion pairs with multiple configurations of the complex anion and the Mg cation whose available orbitalsmore » are partially delocalized over the molecular complex and have antibonding character, the primary factor of the reductive stability is the shape factor of the solvation sphere of the metal cation center and the degree of the convexity of a polyhedron formed by the metal cation and its coordinating atoms. We focused specifically on the details of Mg (II) bis(trifluoromethanesulfonyl)imide in diethylene glycol dimethyl ether (Mg(TFSI) 2)/diglyme) and its singly charged ion pair, MgTFSI +. In particular, we found that both stable (MgTFSI) + and (MgTFSI) 0 ion pairs have the same TFSI configuration but drastically different solvation structures in the bulk solution. This implies that the MgTFSI/dyglyme reductive stability is ultimately determined by the relative time scale of the solvent dynamics and electron transfer at the Mg–anode interface. In the vicinity of the anode surface, steric factors and hindered solvent dynamics may increase the reductive stability of (MgTFSI) + ion pairs at lower overpotential by reducing the metal cation coordination, in stark contrast to the reduction at high overpotential accompanied by TFSI decomposition. By examining other solute/solvent combinations, we conclude that the electrolytes with highly coordinated Mg cation centers are more prone to reductive instability due to the chemical decomposition of the anion or solvent molecules. Finally, the obtained findings disclose critical factors for stable electrolyte design and show the role of interfacial phenomena in reduction of multivalent ions.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baskin, Artem; Prendergast, David

In this paper, we reveal the general mechanisms of partial reduction of multivalent complex cations in conditions specific for the bulk solvent and in the vicinity of the electrified metal electrode surface and disclose the factors affecting the reductive stability of electrolytes for multivalent electrochemistry. Using a combination of ab initio techniques, we clarify the relation between the reductive stability of contact-ion pairs comprising a multivalent cation and a complex anion, their solvation structures, solvent dynamics, and the electrode overpotential. We found that for ion pairs with multiple configurations of the complex anion and the Mg cation whose available orbitalsmore » are partially delocalized over the molecular complex and have antibonding character, the primary factor of the reductive stability is the shape factor of the solvation sphere of the metal cation center and the degree of the convexity of a polyhedron formed by the metal cation and its coordinating atoms. We focused specifically on the details of Mg (II) bis(trifluoromethanesulfonyl)imide in diethylene glycol dimethyl ether (Mg(TFSI) 2)/diglyme) and its singly charged ion pair, MgTFSI +. In particular, we found that both stable (MgTFSI) + and (MgTFSI) 0 ion pairs have the same TFSI configuration but drastically different solvation structures in the bulk solution. This implies that the MgTFSI/dyglyme reductive stability is ultimately determined by the relative time scale of the solvent dynamics and electron transfer at the Mg–anode interface. In the vicinity of the anode surface, steric factors and hindered solvent dynamics may increase the reductive stability of (MgTFSI) + ion pairs at lower overpotential by reducing the metal cation coordination, in stark contrast to the reduction at high overpotential accompanied by TFSI decomposition. By examining other solute/solvent combinations, we conclude that the electrolytes with highly coordinated Mg cation centers are more prone to reductive instability due to the chemical decomposition of the anion or solvent molecules. Finally, the obtained findings disclose critical factors for stable electrolyte design and show the role of interfacial phenomena in reduction of multivalent ions.« less

Structural modulation of nanowire interfaces grown over selectively disrupted single crystal surfaces

NASA Astrophysics Data System (ADS)

Garratt, E.; Nikoobakht, B.

2015-08-01

Recent breakthroughs in deterministic approaches to the fabrication of nanowire arrays have demonstrated the possibility of fabricating such networks using low-cost scalable methods. In this regard, we have developed a scalable growth platform for lateral fabrication of nanocrystals with high precision utilizing lattice match and symmetry. Using this planar architecture, a number of homo- and heterostructures have been demonstrated including ZnO nanowires grown over GaN. The latter combination produces horizontal, epitaxially formed crystals aligned in the plane of the substrate containing a very low number of intrinsic defects. We use such ordered structures as model systems in the interests of gauging the interfacial structural dynamics in relation to external stimuli. Nanosecond pulses of focused ion beams are used to slightly modify the substrate surface and selectively form lattice disorders in the path of nanowire growth to examine the nanocrystal, namely: its directionality and lattice defects. High resolution electron microscopies are used to reveal some interesting structural effects; for instance, a minimum threshold of surface defects that can divert nanowires. We also discuss data indicating formation of surface strains and show their mitigation during the growth process.

Comparative Analysis of the Reinforcement of Polymers with 2D-Nanofillers: Organoclay and Boron Nitride

NASA Astrophysics Data System (ADS)

Kozlov, G. V.; Kuvshinova, S. A.; Dolbin, I. V.; Koifman, O. I.

2018-03-01

Using the percolation reinforcement model, it has been shown that the main factor governing the degree of reinforcement of polymer/2D-nanofiller composites is the ability of a nanofiller to generate interfacial regions. This parameter is interrelated with two fundamental structural characteristics of a nanocomposite, i.e., the fractal dimension of its structure and the content of polymer matrix/nanofiller interfacial surfaces. The negative effect of high nanofiller anisotropy on the elasticity modulus of a nanocomposite is demonstrated.

Food grade duplex emulsions designed and stabilised with different osmotic pressures.

PubMed

Pawlik, Aleksandra; Cox, Philip W; Norton, Ian T

2010-12-01

In this study we have investigated the production of food grade W(1)/O/W(2) duplex emulsions with salt partitioned into one water phase but not the other. Investigations were carried out with and without balancing osmotic pressures with glucose. A stable 30% primary W(1)/O emulsions containing salt could be produced with more than or equal to 2% polyglycerol polyricinoleate (PGPR) in the oil phase. We suggest that the addition of salt strengthens the interactions between surfactant molecules in the adsorbed film. This is supported by interfacial viscosity and elasticity measurements both of which increased on addition of salt and the fact that in the presence of salt the emulsion was more stable. These simple emulsions were then processed to construct duplex emulsions. When osmotic pressures were balanced with glucose there was still a release of salt in storage. The extent and rate of release was proportional to glucose concentration. This effect was followed over a period of 60days. These data suggest that the release is driven by the chemical potential difference between the two water compartments rather than the unbalanced osmotic pressures. These observations are explained in the context of a water structuring effect from the added glucose, which lowers the interfacial tension of oil-water interface and thus facilitates micellar transport of hydrated salt ions across the oil layer. Copyright © 2010 Elsevier Inc. All rights reserved.

Fabrication and characterization of branched carbon nanostructures.

PubMed

Malik, Sharali; Nemoto, Yoshihiro; Guo, Hongxuan; Ariga, Katsuhiko; Hill, Jonathan P

2016-01-01

Carbon nanotubes (CNTs) have atomically smooth surfaces and tend not to form covalent bonds with composite matrix materials. Thus, it is the magnitude of the CNT/fiber interfacial strength that limits the amount of nanomechanical interlocking when using conventional CNTs to improve the structural behavior of composite materials through reinforcement. This arises from two well-known, long standing problems in this research field: (a) inhomogeneous dispersion of the filler, which can lead to aggregation and (b) insufficient reinforcement arising from bonding interactions between the filler and the matrix. These dispersion and reinforcement issues could be addressed by using branched multiwalled carbon nanotubes (b-MWCNTs) as it is known that branched fibers can greatly enhance interfacial bonding and dispersability. Therefore, the use of b-MWCNTs would lead to improved mechanical performance and, in the case of conductive composites, improved electrical performance if the CNT filler was better dispersed and connected. This will provide major benefits to the existing commercial application of CNT-reinforced composites in electrostatic discharge materials (ESD): There would be also potential usage for energy conversion, e.g., in supercapacitors, solar cells and Li-ion batteries. However, the limited availability of b-MWCNTs has, to date, restricted their use in such technological applications. Herein, we report an inexpensive and simple method to fabricate large amounts of branched-MWCNTs, which opens the door to a multitude of possible applications.

Ionic liquids-water interfacial preparation of triangular Ag nanoplates and their shape-dependent antibacterial activity.

PubMed

Lu, Weiwei; Yao, Kaisheng; Wang, Jianji; Yuan, Jiongliang

2015-01-01

As a class of green and designable solvents, ionic liquids (ILs) have been used extensively in inorganic synthesis. In those schemes, ILs were usually used as reaction media to replace water and organic solvents, and/or used as stabilizer and capping agents to act like an amphiphilic molecule or polymer. However, the unique properties of ILs were not fully utilized in the area of material preparation. In this study, a new protocol of "ILs-water interfacial synthesis" was developed and used for the preparation of Ag nanomaterials. Taking the advantage of tunable property of ILs-water interface, Ag nanomaterials with different morphology such as triangular nanoplates, polygonal nanoplates, and nanoparticles could be facilely obtained. Growth mechanism of the triangular Ag nanoplates has been investigated from structural characterization and molecular dynamics (MD) simulation. It was shown that growth of the nanoplates was under kinetic control mainly due to high viscosity and ionicity of the ILs. Furthermore, the antimicrobial performance of these Ag samples was tested to study the influence of shape of the Ag nanomaterials on the antimicrobial activity and the related antimicrobial mechanism. The results suggested that the efficient antimicrobial activity of the triangular Ag nanoplates was ascribed to their sharp corners and edges and large areas of active (111) crystal plane, which leads to the higher amount of leaching Ag(+) ion. Copyright © 2014 Elsevier Inc. All rights reserved.

Effect of pendent chains on the interfacial properties of thin polydimethylsiloxane (PDMS) networks.

PubMed

Landherr, Lucas J T; Cohen, Claude; Archer, Lynden A

2011-05-17

The interfacial properties of end-linked polydimethylsiloxane (PDMS) films on silicon are examined. Thin cross-linked PDMS films (∼10 μm thick) were synthesized over a self-assembled monolayer supported on a silicon wafer. By systematically varying the concentration of monofunctional PDMS in a mixture with telechelic precursor molecules, structures ranging from near-ideal elastic networks to poorly cross-linked networks composed of a preponderance of dangling/pendent chains were synthesized. Lateral force microscopy (LFM) employing bead probes was used to quantify the effect of network structure on the interfacial friction coefficient and residual force. Indentation measurements employing an AFM in force mode were used to characterize the elastic modulus and the pull-off force for the films as a function of pendent chain content. These measurements were complemented with conventional mechanical rheometry measurements on similar thick network films to determine their bulk rheological properties. All networks studied manifested interfacial friction coefficients substantially lower than that of bare silicon. PDMS networks with the lowest pendent chain content displayed friction coefficients close to 1 order of magnitude lower than that of bare silicon, whereas networks with the highest pendent chain content manifested friction coefficients about 3 times lower than that of bare silicon. At intermediate sliding velocities, a crossover in the interfacial friction coefficient was observed, wherein cross-linked PDMS films with the least amount of pendent chains exhibit the highest friction coefficient. These observations are discussed in terms of the structure of the films and relaxation dynamics of elastic strands and dangling chains in tethered network films.

Abnormal Current–Voltage Hysteresis Induced by Reverse Bias in Organic–Inorganic Hybrid Perovskite Photovoltaics

DOE PAGES

Rajagopal, Adharsh; Williams, Spencer T.; Chueh, Chu-Chen; ...

2016-02-29

In this study, reverse bias (RB)-induced abnormal hysteresis is investigated in perovskite solar cells (PVSCs) with nickel oxide (NiOx)/methylammonium lead iodide (CH 3NH 3PbI 3) interfaces. Through comprehensive current-voltage (I-V) characterization and bias-dependent external quantum efficiency (EQE) measurements, we demonstrate that this phenomenon is caused by the interfacial ion accumulation intrinsic to CH 3NH 3PbI 3. Subsequently, via systematic analysis we discover that the abnormal I-V behavior is remarkably similar to tunnel diode I-V characteristics and is due to the formation of a transient tunnel junction at NiO x/CH 3NH 3PbI 3 interfaces under RB. The detailed analysis navigating themore » complexities of I-V behavior in CH 3NH 3PbI 3-based solar cells provided here ultimately illuminates possibilities in modulating ion motion and hysteresis via interfacial engineering in PVSCs. Moreover, this work shows that RB can alter how CH 3NH 3PbI 3 contributes to the functional nature of devices and provides the first steps toward approaching functional perovskite interfaces in new ways for metrology and analysis of complex transient processes.« less

Interfacial charging phenomena of aluminum (hydr)oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiemstra, T.; Yong, H.; Van Riemsdijk, W.H.

1999-08-31

The interfacial charging of Al(OH){sub 3} (gibbsite and bayerite) and Al{sub 2}O{sub 3} has been studied. For Al(OH){sub 3} it can be shown that the very strong variation in charging behavior for different preparations is related to the relative presence of differently reacting crystal planes. The edge faces of the hexagonal gibbsite crystals are proton reactive over the whole pH range, in contrast to the 001 plane, which is mainly uncharged below pH = 10. On this 001 face only doubly coordinated surface groups are found, in contrast to the edges which also have singly coordinated surface groups. The resultsmore » are fully in agreement with the predictions of the Multi site complexation (MUSIC) model. The proton adsorption, electrolyte ion adsorption, and shift of the IEP of gibbsite and aluminum oxide have been modeled simultaneously. For gibbsite, the ion pair formation of Na is larger than that of Cl, as is evidenced by modeling the experimentally observed upward shift on the IEP and charge reversal at high electrolyte concentrations. All these experimental results can be satisfactorily modeled with the MUSIC model, including the experimental surface potential of aluminum oxide (ISFET).« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Segeun; Yoon, Jungjin; Ha, Kyungyeon

The capability of fabricating three dimensional (3-D) nanostructures with desired morphology is a key to realizing effective light-harvesting strategy in optical applications. In this work, we report a novel 3-D nanopatterning technique that combines ion-assisted aerosol lithography (IAAL) and soft lithography that serves as a facile method to fabricate 3-D nanostructures. Aerosol nanoparticles can be assembled into desired 3-D nanostructures via ion-induced electrostatic focusing and antenna effects from charged nanoparticle structures. Replication of the structures with a polymeric mold allows high throughput fabrication of 3-D nanostructures with various liquid-soluble materials. 3-D flower-patterned polydimethylsiloxane (PDMS) stamp was prepared using the reportedmore » technique and utilized for fabricating 3-D nanopatterned mesoporous TiO2 layer, which was employed as the electron transport layer in perovskite solar cells. By incorporating the 3-D nanostructures, absorbed photon-to-current efficiency of >95% at 650 nm wavelength and overall power conversion efficiency of 15.96% were achieved. The enhancement can be attributed to an increase in light harvesting efficiency in a broad wavelength range from 400 to 800 nm and more efficient charge collection from enlarged interfacial area between TiO2 and perovskite layers. This hybrid nanopatterning technique has demonstrated to be an effective method to create textures that increase light harvesting and charge collection with 3-D nanostructures in solar cells.« less

Structure that encapsulates lithium metal for high energy density battery anode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Yi; Yan, Kai; Chu, Steven

A battery includes 1) an anode, 2) a cathode, and 3) an electrolyte disposed between the anode and the cathode. The anode includes a current collector and an interfacial layer disposed over the current collector, and the interfacial layer includes an array of interconnected, protruding regions that define spaces.

Composite Materials for Maxillofacial Prostheses.

DTIC Science & Technology

1980-08-01

projected composite systems are elastomeric-shelled, liquid-filled * microcapsules . Experiments continued on the interfacial polymerization process with...filled microcapsules . Experiments continued on the interfacial polymerization process, with spherical, sealed, capsules achieved. Needs identified are...consists of liquid-filled, elastomeric-shelled microcapsules held together to form a deformable mass; this is to simulate the semi-liquid cellular structure

Interfacial B-site atomic configuration in polar (111) and non-polar (001) SrIrO3/SrTiO3 heterostructures

NASA Astrophysics Data System (ADS)

Anderson, T. J.; Zhou, H.; Xie, L.; Podkaminer, J. P.; Patzner, J. J.; Ryu, S.; Pan, X. Q.; Eom, C. B.

2017-09-01

The precise control of interfacial atomic arrangement in ABO3 perovskite heterostructures is paramount, particularly in cases where the subsequent electronic properties of the material exhibit geometrical preferences along polar crystallographic directions that feature inevitably complex surface reconstructions. Here, we present the B-site interfacial structure in polar (111) and non-polar (001) SrIrO3/SrTiO3 interfaces. The heterostructures were examined using scanning transmission electron microscopy and synchrotron-based coherent Bragg rod analysis. Our results reveal the preference of B-site intermixing across the (111) interface due to the polarity-compensated SrTiO3 substrate surface prior to growth. By comparison, the intermixing at the non-polar (001) interface is negligible. This finding suggests that the intermixing may be necessary to mitigate epitaxy along heavily reconstructed and non-stoichiometric (111) perovskite surfaces. Furthermore, this preferential B-site configuration could allow the geometric design of the interfacial perovskite structure and chemistry to selectively engineer the correlated electronic states of the B-site d-orbital.

Interfacial exchange coupling and magnetization reversal in perpendicular [Co/Ni]N/TbCo composite structures.

PubMed

Tang, M H; Zhang, Zongzhi; Tian, S Y; Wang, J; Ma, B; Jin, Q Y

2015-06-15

Interfacial exchange coupling and magnetization reversal characteristics in the perpendicular heterostructures consisting of an amorphous ferrimagnetic (FI) TbxCo(100-x) alloy layer exchange-coupled with a ferromagnetic (FM) [Co/Ni]N multilayer have been investigated. As compared with pure TbxCo(100-x) alloy, the magnetization compensation composition of the heterostructures shift to a higher Tb content, implying Co/Ni also serves to compensate the Tb moment in TbCo layer. The net magnetization switching field Hc⊥ and interlayer interfacial coupling field Hex, are not only sensitive to the magnetization and thickness of the switched TbxCo(100-x) or [Co/Ni]N layer, but also to the perpendicular magnetic anisotropy strength of the pinning layer. By tuning the layer structure we achieve simultaneously both large Hc⊥ = 1.31 T and Hex = 2.19 T. These results, in addition to the fundamental interest, are important to understanding of the interfacial coupling interaction in the FM/FI heterostructures, which could offer the guiding of potential applications in heat-assisted magnetic recording or all-optical switching recording technique.

Spatially Resolved Imaging on Photocarrier Generations and Band Alignments at Perovskite/PbI2 Heterointerfaces of Perovskite Solar Cells by Light-Modulated Scanning Tunneling Microscopy.

PubMed

Shih, Min-Chuan; Li, Shao-Sian; Hsieh, Cheng-Hua; Wang, Ying-Chiao; Yang, Hung-Duen; Chiu, Ya-Ping; Chang, Chia-Seng; Chen, Chun-Wei

2017-02-08

The presence of the PbI 2 passivation layers at perovskite crystal grains has been found to considerably affect the charge carrier transport behaviors and device performance of perovskite solar cells. This work demonstrates the application of a novel light-modulated scanning tunneling microscopy (LM-STM) technique to reveal the interfacial electronic structures at the heterointerfaces between CH 3 NH 3 PbI 3 perovskite crystals and PbI 2 passivation layers of individual perovskite grains under light illumination. Most importantly, this technique enabled the first observation of spatially resolved mapping images of photoinduced interfacial band bending of valence bands and conduction bands and the photogenerated electron and hole carriers at the heterointerfaces of perovskite crystal grains. By systematically exploring the interfacial electronic structures of individual perovskite grains, enhanced charge separation and reduced back recombination were observed when an optimal design of interfacial PbI 2 passivation layers consisting of a thickness less than 20 nm at perovskite crystal grains was applied.

Liquid-Vapor Interfacial Properties of Aqueous Solutions of Guanidinium and Methyl Guanidinium Chloride: Influence of Molecular Orientation on Interface Fluctuations

PubMed Central

Ou, Shuching; Cui, Di; Patel, Sandeep

2014-01-01

The guanidinium cation (C(NH2)3+) is a highly stable cation in aqueous solution due to its efficient solvation by water molecules and resonance stabilization of the charge. Its salts increase the solubility of nonpolar molecules (”salting-in”) and decrease the ordering of water. It is one of the strongest denaturants used in biophysical studies of protein folding. We investigate the behavior of guanidinium and its derivative, methyl guanidinium (an amino acid analogue) at the air-water surface, using atomistic molecular dynamics (MD) simulations and calculation of potentials of mean force. Methyl guanidinium cation is less excluded from the air-water surface than guanidinium cation, but both cations show orientational dependence of surface affinity. Parallel orientations of the guanidinium ring (relative to the Gibbs dividing surface) show pronounced free energy minima in the interfacial region, while ring orientations perpendicular to the GDS exhibit no discernible surface stability. Calculations of surface fluctuations demonstrate that near the air-water surface, the parallel-oriented cations generate significantly greater interfacial fluctuations compared to other orientations, which induces more long-ranged perturbations and solvent density redistribution. Our results suggest a strong correlation with induced interfacial fluctuations and ion surface stability. These results have implications for interpreting molecular-level, mechanistic action of this osmolyte’s interaction with hydrophobic interfaces as they impact protein denaturation (solubilization). PMID:23937431

Plasmonic engineering of metal-oxide nanowire heterojunctions in integrated nanowire rectification units

NASA Astrophysics Data System (ADS)

Lin, Luchan; Zou, Guisheng; Liu, Lei; Duley, Walt W.; Zhou, Y. Norman

2016-05-01

We show that irradiation with femtosecond laser pulses can produce robust nanowire heterojunctions in coupled non-wetting metal-oxide Ag-TiO2 structures. Simulations indicate that joining arises from the effect of strong plasmonic localization in the region of the junction. Strong electric field effects occur in both Ag and TiO2 resulting in the modification of both surfaces and an increase in wettability of TiO2, facilitating the interconnection of Ag and TiO2 nanowires. Irradiation leads to the creation of a thin layer of highly defected TiO2 in the contact region between the Ag and TiO2 nanowires. The presence of this layer allows the formation of a heterojunction and offers the possibility of engineering the electronic characteristics of interfacial structures. Rectifying junctions with single and bipolar properties have been generated in Ag-TiO2 nanowire circuits incorporating asymmetrical and symmetrical interfacial structures, respectively. This fabrication technique should be applicable for the interconnection of other heterogeneous metal-oxide nanowire components and demonstrates that femtosecond laser irradiation enables interfacial engineering for electronic applications of integrated nanowire structures.

Transport of water and solutes in reverse osmosis and nanofiltration membranes

NASA Astrophysics Data System (ADS)

Cahill, David

2009-03-01

The polyamide active layers of reverse osmosis and nanofiltration membranes used for water purification are real-world examples of nanoscale functional materials: the active layer is only ˜100 nm thick. Because the active layer is formed by a process of interfacial polymerization, the structure and composition of the membrane is highly inhomogeneous and even such basic physical and chemical properties as the atomic density, swelling in water, the distribution of charged species between water and membrane, and the mobility of water and ions, are poorly understood. We are using Rutherford backscattering spectrometry (RBS) to determine the composition, roughness, and thickness of the membrane; reveal the surprisingly high solubility of salt ions in the polymer active layer; analyze the acid-base chemistry of charged functional groups; and determine the degree of polymer cross-linking. Measurements of mass-uptake and adsorption-induced mechanical stress of membranes in humid air enable us to determine the water solubility, specific volume of water, and the mechanical strength of the membrane. Comparisons between these equilibrium data and the permeability of the membrane to water and salts show that the mobility of water molecules in the membrane approaches the mobility of bulk water, and that the rejection of salt ions is accomplished by low mobility, not low solubility. My collaborators in this work are Xijing Zhang, Orlando Coronell, and Prof. Benito Mariñas.

Novel three-dimensionally ordered macroporous Fe3+-doped TiO2 photocatalysts for H2 production and degradation applications

NASA Astrophysics Data System (ADS)

Yan, Xiaoqing; Xue, Chao; Yang, Bolun; Yang, Guidong

2017-02-01

Novel three-dimensionally ordered macroporous (3DOM) Fe3+-doped TiO2 photocatalysts were prepared using a colloidal crystal template method with low-cost raw material including ferric trichloride, isopropanol, tetrabutyl titanate and polymethyl methacrylate. The as-prepared 3DOM Fe3+-doped TiO2 photocatalysts were characterized by various analytical techniques. TEM and SEM results showed that the obtained photocatalysts possess well-ordered macroporous structure in three dimensional orientations. As proved by XPS and EDX analysis that Fe3+ ions have been introduced TiO2 lattice and the doped Fe3+ ions can act as the electron acceptor/donor centers to significantly enhance the electron transfer from the bulk to surface of TiO2, resulting in more electrons could take part in the oxygen reduction process thereby decreasing the recombination rate of photogenerated charges. Meanwhile, the 3DOM architecture with the feature of interfacial chemical reaction active sites and optical absorption active sites is remarkably favorable for the reactant transfer and light trapping in the photoreaction process. As a result, the 3DOM Fe3+-doped TiO2 photocatalysts show the considerably higher photocatalytic activity for decomposition of the Rhodamine B (RhB) and the generation of hydrogen under visible light irradiation due to the synergistic effects of open, interconnected macroporous network and metal ion doping.

Improvement in the breakdown endurance of high-κ dielectric by utilizing stacking technology and adding sufficient interfacial layer.

PubMed

Pang, Chin-Sheng; Hwu, Jenn-Gwo

2014-01-01

Improvement in the time-zero dielectric breakdown (TZDB) endurance of metal-oxide-semiconductor (MOS) capacitor with stacking structure of Al/HfO2/SiO2/Si is demonstrated in this work. The misalignment of the conduction paths between two stacking layers is believed to be effective to increase the breakdown field of the devices. Meanwhile, the resistance of the dielectric after breakdown for device with stacking structure would be less than that of without stacking structure due to a higher breakdown field and larger breakdown power. In addition, the role of interfacial layer (IL) in the control of the interface trap density (D it) and device reliability is also analyzed. Device with a thicker IL introduces a higher breakdown field and also a lower D it. High-resolution transmission electron microscopy (HRTEM) of the samples with different IL thicknesses is provided to confirm that IL is needed for good interfacial property.

Ion irradiation of the native oxide/silicon surface increases the thermal boundary conductance across aluminum/silicon interfaces

NASA Astrophysics Data System (ADS)

Gorham, Caroline S.; Hattar, Khalid; Cheaito, Ramez; Duda, John C.; Gaskins, John T.; Beechem, Thomas E.; Ihlefeld, Jon F.; Biedermann, Laura B.; Piekos, Edward S.; Medlin, Douglas L.; Hopkins, Patrick E.

2014-07-01

The thermal boundary conductance across solid-solid interfaces can be affected by the physical properties of the solid boundary. Atomic composition, disorder, and bonding between materials can result in large deviations in the phonon scattering mechanisms contributing to thermal boundary conductance. Theoretical and computational studies have suggested that the mixing of atoms around an interface can lead to an increase in thermal boundary conductance by creating a region with an average vibrational spectra of the two materials forming the interface. In this paper, we experimentally demonstrate that ion irradiation and subsequent modification of atoms at solid surfaces can increase the thermal boundary conductance across solid interfaces due to a change in the acoustic impedance of the surface. We measure the thermal boundary conductance between thin aluminum films and silicon substrates with native silicon dioxide layers that have been subjected to proton irradiation and post-irradiation surface cleaning procedures. The thermal boundary conductance across the Al/native oxide/Si interfacial region increases with an increase in proton dose. Supported with statistical simulations, we hypothesize that ion beam mixing of the native oxide and silicon substrate within ˜2.2nm of the silicon surface results in the observed increase in thermal boundary conductance. This ion mixing leads to the spatial gradation of the silicon native oxide into the silicon substrate, which alters the acoustic impedance and vibrational characteristics at the interface of the aluminum film and native oxide/silicon substrate. We confirm this assertion with picosecond acoustic analyses. Our results demonstrate that under specific conditions, a "more disordered and defected" interfacial region can have a lower resistance than a more "perfect" interface.

Effects of interfacial layer on characteristics of TiN/ZrO2 structures.

PubMed

Kim, Younsoo; Kang, Sang Yeol; Choi, Jae Hyoung; Lim, Jae Soon; Park, Min Young; Chung, Suk-Jin; Chung, Jaegwan; Lee, Hyung Ik; Kim, Ki Hong; Kyoung, Yong Koo; Heo, Sung; Yoo, Cha Young; Kang, Ho-Kyu

2011-09-01

To minimize the formation of unwanted interfacial layers, thin interfacial layer (ZrCN layer) was deposited between TiN bottom electrode and ZrO2 dielectric in TiN/ZrO2/TiN capacitor. Carbon and nitrogen were also involved in the layer because ZrCN layer was thermally deposited using TEMAZ without any reactant. Electrical characteristics of TiN/ZrO2/TiN capacitor were improved by insertion of ZrCN layer. The oxidation of TiN bottom electrode was largely inhibited at TiN/ZrCN/ZrO2 structure compared to TiN/ZrO2 structure. While the sheet resistance of TiN/ZrCN/ZrO2 structure was constantly sustained with increasing ZrO2 thickness, the large increase of sheet resistance was observed in TiN/ZrO2 structure after 6 nm ZrO2 deposition. When ZrO2 films were deposited on ZrCN layer, the deposition rate of ZrO2 also increased. It is believed that ZrCN layer acted both as a protection layer of TiN oxidation and a seed layer of ZrO2 growth.

Aerosol Particle Interfacial Thermodynamics and Phase Partitioning Measurements Using Biphasic Microfluidics

NASA Astrophysics Data System (ADS)

Dutcher, Cari; Metcalf, Andrew

2015-03-01

Secondary organic aerosol particles are nearly ubiquitous in the atmosphere and yet there remain large uncertainties in their formation processes and ambient properties. These particles are complex microenvironments, which can contain multiple interfaces due to internal aqueous-organic phase partitioning and to the external liquid-vapor surface. Interfacial properties affect the ambient aerosol morphology, or internal structure of the particle, which in turn can affect the way a particle interacts with an environment of condensable clusters and organic vapors. To improve our ability to accurately predict ambient aerosol morphology, we must improve our knowledge of aerosol interfaces and their interactions with the ambient environment. Unfortunately, many techniques employed to measure interfacial properties do so in bulk solutions or in the presence of a ternary (e.g. solid) phase. In this talk, a novel method using biphasic microscale flows will be introduced for generating, trapping, and perturbing complex interfaces at atmospherically relevant conditions. These microfluidic experiments utilize high-speed imaging to monitor interfacial phenomena at the microscale and are performed with phase contrast and fluorescence microscopy on a temperature-controlled inverted microscope stage. From these experiments, interfacial thermodynamic properties such as surface or interfacial tension, rheological properties such as interfacial moduli, and kinetic properties such as mass transfer coefficients can be measured or inferred.

Interfacial Bonding Energy on the Interface between ZChSnSb/Sn Alloy Layer and Steel Body at Microscale

PubMed Central

Xia, Quanzhi; Ma, Yang; Meng, Fanning; Liang, Yinan; Li, Zhixiong

2017-01-01

To investigate the performance of bonding on the interface between ZChSnSb/Sn and steel body, the interfacial bonding energy on the interface of a ZChSnSb/Sn alloy layer and the steel body with or without Sn as an intermediate layer was calculated under the same loadcase using the molecular dynamics simulation software Materials Studio by ACCELRYS, and the interfacial bonding energy under different Babbitt thicknesses was compared. The results show that the bonding energy of the interface with Sn as an intermediate layer is 10% larger than that of the interface without a Sn layer. The interfacial bonding performances of Babbitt and the steel body with Sn as an intermediate layer are better than those of an interface without a Sn layer. When the thickness of the Babbitt layer of bushing is 17.143 Å, the interfacial bonding energy reaches the maximum, and the interfacial bonding performance is optimum. These findings illustrate the bonding mechanism of the interfacial structure from the molecular level so as to ensure the good bonding properties of the interface, which provides a reference for the improvement of the bush manufacturing process from the microscopic point of view. PMID:28946690